I use a window and 16 hrs. of supplemental light . These plants are 6 weeks from planting the seed. Ive used a greenhouse in lots of past years but this works better. Temp. between 75 and 80 and no aphids . Sun through a window on its own is not enough bot with supplemental light it works like a charm. Heating a greenhouse can be your biggest expense. Had one 36 by 96 and it cost $130 a week and the aphids were a constant battle. I have more seed then I know what to do with check my list and send me an email. A window sill with supplemental light is the way to go unless your doing hundreds of plants. I also use a Bloom fertilizer half strength once a week to promote roots opposed to leaves. I think it makes for a stronger plant

They look fine now. I was also thinking that the lack of nutrients(especially Nitrogen) was the reason for yellow pale color. And as it was pointed out chunky, partially composted mater can absorb the nutrient an then will release them later on as they get fully composted. This feaure is consider as a plus(+) in moderate amounts as ait regulates nutriens to the plants. But with the young plants, when the fertilizers is supplied in low amounts, then they end up gettinh NOTHING much. Now I see another problem: THAT CONTAINER MIGHT BE A BIT TOO SMALL FOR 4 PLANTS. They don't seem to have enough head room.

Two major changes topping the plant and adding to that the environmental change with switching the light source. Hard to say exactly the cause of the slow return of growth with deformed and/or crispy leaves. I did read reviews on the LED lighting you are using, I would read the good and bad reviews some even do a side by side comparison with these and MH, worth looking into. Either you can leave it the same over the next few weeks to see how they do or return the old light source and see if they fair better. Let us know how they do. Mark

Diy Guy: Not sure where in the country you are. I gather you started all your crops on April 8th? I find tomatoes to be very fast growing and onions and peppers much slower. For my area (SE WI) I find it best to start onions in early-mid march. They can be pokey. Cut the tips off the tops as they grow as they will flop over otherwise. I normally do this a few times before transplanting them into the garden in May. The stems will get thicker each time you do this and the onions will then be straight up in the flat and not a mess. Give them a haircut whenever they flop. For peppers, I like to start around March 20th. I start my tomatoes April 10-12th every year and they are good to plant out late May. All these dates are relative however to when I need a finished seedling to plant in my garden. You mentioned germination times. My tomatoes took about 7 days to germinate this year. Germination will depend somewhat on soil temps. Since my basement is a bit cold, I always leave my seeded flats upstairs until they germinate then move them under florescent lights in my basement. Peppers are always notoriously slow for me to germinate. Sometimes I have some come up in the flat and a week later others start emerging just when I have given up hope on them. Currently I have transplanted all the tomato seedlings into 1801 cell trays. They have been fertilized once. Growing nicely. I have had to lower them from the lights about every 2-3 days as they increase in height. I plan on putting them outside for a week to harden them off around May 15th before planting in the garden (I will put in the garage at night or bring inside if cold). Normally I put them along my garage where they get a few hours of morning sun only. Every 2 days I move them farther away and into more sunlight. If you don't harden them off first, they can really scorch up after planting outside. Potting mix is very important! I bought some on sale a few years ago and was really unhappy with it. Very fine and did not seem to drain well. My crops grew but the root systems were much less developed upon transplanting than I expected when putting them in the garden. Happily I have used up that worthless brand. Whatever I bought this year is really light, drains well and the tomatoes had deep roots already when I transplanted them to individual pots from the seedling flat at first true leaf. Last year's potting mix also had me fertilizing a lot as the plants would not stay green. My new mix must have a wetting agent in it as it was easy to get wet right out of the package and really healthy plants this year. Just an FYI that not all potting mixes on the market are equal in performance.