I started these (see pix) from seed, transplanted them into peat pots a few weeks ago, and have been taking them outside for fresh air and sun during the day. The second leaves on about half my plants started getting papery brown spots, with a few of them beginning to wither. Does this look like overwatering? Underwatering? Temperature stress from the ups and downs? A few nights, I left them on the porch after sunset and it got into the low fifties. The house is usually around 68 degrees. Thanks so much! I hope it's not a fungus or something.
Advice on tomato seedlings
They look good. It might be sun scald on those dewy lower leaves as you are hardening them off. You should remove leaves from the lower third and sink the pots when you plant out so no loss. Young tomatoes are fine with temperatures in the low fifties. Some, including myself, think occasional mid-forties nights make for more robust plants. We'll be forty-six tonight and I have twenty-four plants in.
Thank you so much, MaypopLaurel, for putting my mind at ease! My nightmare is introducing a fungus to the garden, but I noticed the same papery brown spots on another kind of seedling, so I think you're right about sun scald.
Diseases and tomatoes go hand in hand. Accept that or have lots of sleepless nights. It's seems the way vegetable gardening goes...you have a healthy plant and by the time it is fruiting you are also dealing with disease. The goal is to be one step ahead.
Cut bottom leaves that look questionable and remove debris throughout the growing season, mulch after soil warms and nighttime temps are above fifty to avoid soil splash. Water plants at their base, not the leaves.
We had a freak hailstorm in my tiny corner of north Georgia the day after I posted to your question. I had twenty-four tomatoes in the ground at the time. Peppers too. Everything was either pelted or covered in an inch, or more, of ice for several hours. I lost only two tomatoes. They're tough. We are broaching eighty days but will have two nights this week in the mid to low forties. I have thirty-nine tomatoes in now.