Tobacco mosaic virus is very rare (but possible) but I'd first suspect the more likely villains. Do the spots rub off? If so the problem is a mold from too much moisture. Have you been misting the plants? If so, stop and see if the spots disappear. Is there adequate air circulation? A small fan on low will help greatly. Under lights? Need to be close but not close enough to scorch. Room temps? Lettuce prefers cool temps and thrives in the 50 degree range. Lastly any chance they are a pest? Aphids come to mind as a common problem with lettuce seedlings. If they can be flicked off the leaves think aphids. With the Jiffy mix you won't have any N burn going (another possibility sometimes) but you will need to feed them as it has no nutrients. A 25% solution of a water soluable fertilizer works well - nothing stronger. Hope some of this helps. Dave

maybe some sunburn.. if it went from a rather dark spot to the sun ... pull it away from the window a bit ... and perhaps.. with the sun insult.. maybe it needs a BIT more water ... you can root pieces very fast with this plant ... so why not try a piece when you have a big enough plant ... i cant tell whats going on with the pic.. is that a straight down pic on a table.. or what ... maybe a pic a bit further away and not straight down will help us spot something else ... welcome to the forums ... ken

If this plant can go more than 2 weeks between waterings w/o wilting, it's almost a certainty that there is a lot of potential for growth and vitality left lying on the table; and, mixing perlite into the soil does very little to improve drainage or aeration. Perlite's main attribute is, it displaces soil that would otherwise be filled with water after a thorough watering. Let's say you have a gallon can filled to the top with your soil (before the perlite was added). Between all the fine soil particles, there is some air. Incorporate a marble into the soil. What happens? A volume of soil and air equal to the volume of the marble is displaced and spills out of the pot. Now do that 500 times, so you now have a can of soil that's roughly half marbles and half your original soil. The 2 things that jump out at us are 1) the roots cannot grow into the marble, so the amount of soil available for root colonization is now half of what it was. 2) The amount of air in the gallon of soil + marbles is half that of the gallon of soil. So what is the net effect? By adding the marbles, you simply reduce the amount of soil the plant can actually grow in . Perlite is no different than the marbles, except that, the rough surface of the perlite does add a small amount of aeration in the immediate vicinity of the particle; however, since it's impossible for the particle to provide more aeration than the volume of soil it displaces, the o/a volume of air porosity in the mix of your soil + perlite decreased, and will continue to decrease on a per volume basis until there is so much perlite in the mixture there is no longer enough fine particles from your mixture to fill all the air spaces between the perlite particles - the 'threshold proportion'. From that point on, when perlite is coarse and the overwhelmingly large fraction of the medium (>80%), air porosity increases quickly. You can see this threshold effect clearly by starting with 2" of water in a jar. As you add marbles to the jar, the volume of the mixture decreases, but the air porosity remains at 0. If we keep adding marbles, at some point there will not be enough water to fill the very large spaces between the marbles, so at that point, the threshold proportion, air porosity increases rapidly. The take-away is, if you want to take advantage of the significantly better opportunity highly aerated and fast draining media offer plants, it's essential to start with a large fraction of coarse material, and limit fine material smaller than 1/10" to being used as a way to adjust water retention of the medium to something you are comfortable with. If you had a medium that required watering every day, your plants would love it, even if you wouldn't want to tolerate the extra effort. I don't want to confuse you with informational overload, but I do want you to have a sense of how important growing in a medium that doesn't fight you tooth and nail for control of your plant's vitality. If you like, we can talk more about how to make or find a good grow medium. ****************************************************************************************** Your plant should be watered before it becomes "stone dry"; and, if you really ARE allowing it to become that dry, it would show signs of wilting. If it's not wilting, it's not stone dry. A good way to determine proper watering intervals is by using a 'tell'. Using a 'tell' Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant. Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor. In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water. Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'. One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue. Al

Overwatering is the #1 cause of death of these plants. It pays to keep it in a pot with soil amended with perlite or pulmace or both. Some of my Aloes I keep in a 50/50 mix of potting soil and perlite. From what I can see, it still looks good. Give it all the indoor sun you can.