milocrab, you have got me all over the globe - Hong Kong, Asia, Australia! About your seedlings; the growing medium appears too heavy for a tiny mustard seed and you may have compounded the problem by your watering program. A seed needs to be in a moist environment to imbibe moisture in its own sweet time. If the medium is too wet the seed will rot. As the seed germinates it uses up its stored energy to produce a root and shoot. These are necessarily small, definitely immature and very sensitive to the environment. Application of fertilizer and exposure to (sun)light must be done carefully and gradually or the seedling can easily die. All of the leaves in the photographs show a nutritional problem; either a shortage of elements or else a problem with uptake if the elements are present. Overwatering can prevent uptake by displacing oxygen at root level The bleached areas on some leaves can be caused by sudden and perhaps extreme exposure to (sun)light; or damage due to the activity of the "blotch" (as opposed to the "serpentine") leafminer. 91ðF "even for one hour" to us can mean "for an entire hour?" to a seedling as it pulls on all of its meagre reserves to cope with this environmental stress. Allow me to reproduce from memory, a poem by Kate Brown from my kindergarten school days. "In the heart of a seed, buried deep, so deep; A dear little plant lay fast asleep. "Wake!" said the sunshine, "and creep to the light". "Wake!" said the voice of the raindrops bright. The little plant heard it And rose to see. What the wonderful Outside world might be." We had to mime as we recited and it is a pleasamt memory.

MVIsland, the diagnosis of your problem was INTERVENAL Chlorosis ... lacey yellowing between the veins of the leaves ... caused by micronutrient deficiencis, usually iron or magnesium. That is why I recommended Ironite or Fertilome iron supplement. Also, as Mulio said, a good Miracle Gro type tomato food should contain all those micronutrients, but I recommended the Ironite + Epsoms salts as a booster. What Elskunkito describes sounds more like classic nitrogen deficiency caused or compounded by chronic wet root ball causing rotted roots which then cannot take up sufficient nitrogen and phosphorus (he noted some stiff purple stems along with the gradually yellowing leaves). Without pictures, I cannot confirm the diagnosis, just the same as I needed pictures of your plants to confirm micronutrient deficiency witnessed by intervenal chlorosis. However, what elskunkito describes, and he describes it quite well, SOUNDS LIKE gradual and general chlorosis moving from the lower and outer extremes upward through the plant. Why is this nitrogen deficiency (most likely)? Because nitrogen is mobile in the plant. That is, the plant is capable of moving nitrogen from where it is least needed (the cotyledons and lower, older leaves) and transporting it to where it is most needed (the growing tips). Nitrogen is essential for photosynthesis, cell division, new growth and starch (sugar) production. Why is there no nitrogen left in the old potting soil? Because nitrogen is volatile and evaporates into the atmosphere or is washed out of the potting mix by irrigation. Nitrogen must be replenished into the soil in regular dosings for proper plant health. Lastly, folks who continually repeat the old saw that seedlings do not require fertilizer are doing no one any favors. Stop it please. This instance with elskunkito's excellent description of symptoms as well as MVIsland's previous problem two weeks ago are just 2 recent instances that clearly prove growing tomato plants require proper nutrient feedings. In elskunkito's case, he clearly stated his plants are 8 - 10 inches tall with minimum 3 sets of true leaves ... and "a couple months old." THEY NEED PLANT FOOD!!! My caution to you all is to ignore these folks who repeatedly say tomato seedlings do not need plant food. They are only repeating bad, incomplete, uneducated information they have gleened from other uninformed or improperly informed people at other websites, IMO.

I don't know what it is, but I once had something similar. I swear my tomatoes got the disease from a tree in my backyard. Are there any spotty leaves on any trees or bushes around?

I think the most likely culprit is epinasty due to overwatering and potentially a soil mix that is too heavy (too much soil/compost in containers can compact and/or get sludgy). The general rule of thumb for watering tomatoes, whether in-ground or in containers, is to dig down into the soil first to see whether it's dry a couple inches down (deeper for in-ground plants) and actually needs water. If the soil surface is still moist, watering is absolutely not needed and could be detrimental. There's also a possibility that the mulch or compost or "farm dirt" could have been contaminated with herbicides, but herbicide injury is usually more distorted looking than that and usually is accompanied by yellowing or other discoloration. You can test this out by planting peas in the soil next to the tomatoes. If the peas germinate and emerge looking normal, herbicide is not the problem. That doesn't look like any of the common viruses to me.