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I started a few varieties of tomato plants inside this year, from seedlings. They are under grow lights, and have heating mats under them (set to 80°F).

Two of the plants have leaves that appear damaged or burned, and one of them has leaves that seem to be wilting.

Until this morning, they were all crowded together into one tray. I split them between two trays to try to give each plant more room and access to light.

I have been keeping the soil damp.

Are these plants OK, or do they require some intervention?

As a followup: it is probably going to be about 3 more weeks until I can safely plant these guys outside. Do I need to replant them in larger pots, or apply some form of plant food?

the overall setup burned or damaged leaf edges one wilted or floppy leaf another burned or damaged leaf

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  • You do not need, nor is it beneficial, to continue applying bottom heat once the seeds have germinated. Put those mats away until you are germinating something else.
    – Ecnerwal
    Commented Apr 9, 2022 at 12:41
  • Thank you, @Ecnerwal. I just turned the heating mats off.. :)
    – negacao
    Commented Apr 9, 2022 at 12:42

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I would normally tell you to repot them into larger pots, but you don't have room for more pots under the lights. You do need to feed your plants! The first closeup shows what appears to be chlorosis but could also be another nutrient deficiency. Whenever leaves turn yellow it's never good. I do not see signs of fungal issues, which is a good thing. I would use a quick-hit fertilizer (one that you dissolve in water which you then use to water the plants) and I'd keep using that fertilizer until you plant the tomatoes outside. I'd also gently remove the yellowing and burned leaves as long as there are green ones coming to replace them.

Don't worry if the plants get too "leggy" - when you plant them, just plant them as deep as possible; they'll put out new roots from the buried stem.

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  • Given that the pots are spaced out in their trays, larger pots don't seem out of the question. Hard to tell from pictures but I'd guess roughly quart pots (I reuse yogurt containers for those) would be enough larger than what they are in to be helpful.
    – Ecnerwal
    Commented Apr 10, 2022 at 1:36
  • I was looking at the tops of the plants, not the size of the pots. As they currently stand, the tops are almost touching. Over the next few weeks the tomatoes will develop into a miniature forest even with the pots that you currently have them in. If you have them in larger pots, it will be even more crowded. This can definitely affect air flow and perhaps lead to other problems. If nothing else, I've found that when tomatoes touch too much then their stems become rather weak and don't stand up well without support when planted (they eventually toughen up, but you don't want them sideways).
    – Jurp
    Commented Apr 10, 2022 at 2:53
  • @Jurp, I did actually manage to get them into slightly bigger pots - they are the size of about 4 of these smaller ones, but they are a little shallower. Next year I will know better and use bigger pots from the start. I can also adjust the height of the lights if the plants get too close. I am hoping to plant them outside in about 20 more days.
    – negacao
    Commented Apr 11, 2022 at 21:25

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