Do what Gorbelly says, they do not look sick... Congrats on your first tomato seed planting.

Agree - no disease. Do as gorbelly recommended above. The peat pots are the primary issue as they encourage you to over-water - thus the yellowing. Then feed them. I hope the MG is the regular potting mix and NOT the MG Garden Soil.

Dave

ditto on the above. do not use peat pots. get rid of them when you pot up. the disposable red solo cups are great, punch some holes in the bottom for drainage. they look great. may you have many fine BLTs ….

Thanks so much everyone! I just got done repotting them to solo cups. They all had quite a lot of roots developed, I was very surprised. Yes, it is regular MG potting mix, not the garden soil. I'm hoping they will turn around and green up a little. It sounds dumb, but I am a little bit emotionally invested in these plants now (lol) and want to see them do well. Looking to plant outside in a few weeks. I will be following all of the steps. I will update if any problems arise. Thanks!

How long do you keep the T5s on?

They don't look sick, to me.

Well, seedlings aren't doing much better. I am attaching a few pictures. All 18 of them have some degree of leaf yellowing, with some of them having all of the leaves being yellow. I have them under a shelter for most of the day now starting the hardening off process, but I am also considering throwing them out and just buying some from a store next week. I did all of the things mentioned above, but nothing changed. The yellowing leaves are eventually turning brown and withering some.

Don't throw them out until you hear from the experts... That could be just some kind of temperature related nutrient deficiency. It would be a terrible shame to toss you first seed grown tomato plants.

eta: might be a combo over-watering and temp stress

Looks to me like an iron or magnesium deficiency. It could be that the
medium needs a supplement, or that the pH is affecting the plant's
ability to make use of available minerals. You could try a shot of Epsom
salts dissolved in water (no more than a tbsp. to a gal.) or go pick up
a bottle of secondary, and micro-nutrient supplement.

The most common secondary deficiency is mg. The epsom salts will help, but a product formulated with the secondary and micro-nutrients is the better fix. If they are going into the ground eventually, the problem will probably fix itself, but for now, they need the secondary/micro-nutrients to keep them alive and healthy.

If it's a pH issue, that's another thing all together.

" I did all of the things mentioned above, "

It is clearly a nutrient issue. What and how much exactly did you feed them? gorbelly outlined all the feeding steps in his post above. What mix exactly is in the pots? How often are you watering?

Dave

Are they still growing despite the yellowing? Do you keep them outside and what are the conditions like temp and exposure to full sun, your watering schedule? Some more details will help. I have been starting my tomato from seed for a number of years and I also purchase plants from the nursery. I've had about 2 plants get some sort of sickness and decline and they were both purchased plants. Most times the seedlings will grow out of the problem and or adjust to warming temps. Tomatoes are some of the easiest plants to start from seed... too soon to give up.

eta: my seedling have turned purple-ish in years past. Turns out to be a nutrient deficiency caused by too cold of temp. They grow out of it but it is shocking to see...

They are not kept outside completely. For the last few days I have had them in a shady spot outside during the day to start hardening them off. Daytime temps are 70-75 degrees here, nights 50-55. I have used an epsom salt mix of 1 tbs/gallon of water. I have fed them twice now with a 1/3 strength solution of MG water soluble fertilizer. I am bottom watering them, about every 5 days or whenever the soil mostly dries out. Some are worse than others with the yellowing.

Here is one I think is a pretty little plant for the most part.

Pic #2 shows signs of sun- or wind-burn. The rest seem to be having continued nutritional problems. Your medium looks very wet. How often are you watering?

If you're close to planting out, I would keep the plants and just plant them out. They're not diseased. They're having nutritional issues--something about their current potting conditions is making them unhappy. It could be a combination of overwatering and overfertilizing.

They should recover quickly once in the ground. If the new growth doesn't start looking good after a week in the ground, you should consider replacement plants, but, IMO, it's too early to give up on them now.

They are being bottom watered about once a week. Not sure how the sun burn has happened unless it was when they got about an inch from my grow light a little while back. They were watered this morning actually, so yes it is a little moist right now. The cups have large drainage holes I punched in the bottom. If they aren't draining well I don't know what else to do about it. I only fertilized in order to see if it would help the nutritional problem. Even then it was very diluted. I don't know, I'm pretty frustrated with them.

I would go with what gobelly says, gobelly is very knowledgeable. They don't look sick to me but are struggling for some reason. Your temps sound good for moving them outside and planting. Good luck...

I've stopped fertilizing my little seedlings and just been adding a layer of compost to the top of the potting soil and I water from the top which most experts do not recommend. I've had problems in the past and suspected there was a problem with my fertilizing. I like to use a good potting soil with the compost then I wait to add fertilizer until after I plant in the ground.

Just occurred to me to ask... did you use this potting soil?

Miracle-Gro® Moisture Control® Potting Mix

I've read a lot people have problems with this one....

Peat based soils have issues...and promote iron and magnesium deficiencies due to the Ph.

Like they said, plant them outside if weather allows...and they'll be fine. Try to remove as much peat based soil as you safely can just to be sure. Don't bare root them, just remove excess soil that doesn't have roots in it.

ghsides: Not sure how the sun burn has happened

You mentioned you were hardening them off. You have them in a shady spot, but it's possible some direct sun got through. Basically, that white patch that looks thin and papery and that slowly turns tan/brown is how sunburn/windburn classically presents. In the first stages of hardening off, even a short exposure to direct sun rays can cause burn very quickly. It's not a big deal. Happens to all of us from time to time as we're hardening off plants. I just wanted to give you a heads up that the white, dry patches that turn brown are probably sunburn and not related to the other nutritional issue.

Gotcha on the sunburn! Thanks for all of the replies and advice folks. About the Miracle Grow moisture control, no, it is just the standard MG potting mix, nothing special. I've learned a lot through this dilemma with these plants lol

Hope you come back with an update....

rhoder: I would go with what gobelly says, gobelly is very knowledgeable.

I've learned a lot from the oldtimers here. And I'm just the kind of person that researches things obsessively when I'm interested in them, takes lots of notes and observations, and experiments with things.

I just type faster than Dave, Carolyn, Barrie, nctomatoman, seysonn, ted, hudson, janice, labradors, and many many others who more growing experience than I do.

gorbelly I couldn't agree with you more... There is a huge HUGE amount of knowledge here on tomatogrowing and the generosity in taking the time to share the information is astounding to me. I've learned a lot from this forum....

I don't know how much Jiffy Seed Starting Mix you used, but that is devoid of nutrients... and not very good stuff.

I agree with the better experts, it looks to me like a micronutrient deficiency. Alas Miracle Gro fertilizer does not contain magnesium and it is a fair guess your plants need it.

I also agree I would just plant those puppies if it is safe. They should perk up that way eventually.

Ok picking up an old thread. Wondering if the OP can tell us how the seedlings did? Did they survive?

I tried starting from seed this past summer and suffered every calamity but hail and locusts. Researching to do better next year.

Sometimes recounting experiences helps to teach for next time.