Sorry, too little info to make suggestions. Need the following info at the very least.

- Any drainage in that container?

- What did you fill the container with? Soil? Potting mix? What?

- What temperatures have the tomato been exposed to?

- What kind of light?
- And for how many hours a day?

Sorry, here's my response to your questions:

I have drainage holes, it's filled with peat moss and perlite, the temp is consistently around 70-73 Fahrenheit, and it sits under 2 4ft long 6500k 40 watt shop fluorescents.

I planted another rutger at the same time with the same potting mix plus worm castings and its doing much better, but the leaves on that one is also beginning to yellow.

Too wet most likely so cut back on the watering and let the soil dry out more between waterings. Any sign of fungus gnats? Don't feed it with every watering, just 1x a week and see if it improves.

Dave

The plant looks fairly OK to me. Looks like it could be some blight. I'd clip off the damaged leaves and reduce the watering as recommended.

When growing in a cup, you really don't need drainage holes because you shouldn't be watering enough for it to run out the bottom. Just give a small amount of water each day. Just enough to puddle slightly around the stem when you add the water. That's basically a quick tip of water and that's it.

Don't water for two days and then just give it a little drink daily.

I'm sorry but I have to disagree with daily watering. Having drainage holes in most any container is commonly recommended and there honestly is no reason to NOT have them.

Unlike container plants grown outside exposed to greater heat , very few indoor-grown plants, if any, require daily watering unless they are rootbound in the container. In that case they need to be transplanted to a larger container.

Add to that the well-documented fact that frequent, small amounts of water only encourages shallow rooted plants. I'd suggest some further research into this topic.

Dave

That's what I do. I have yet to have damping off or any disease yet and the roots grow quite well. In fact, I will sometimes have leaves droop because they require more water. This is in spite of the fact that temps range between 45 and 65 degrees as they go without heat much of the time in Jan through March..

Most people will give too much water so it probably is not a great idea for the average person who will overwater..

It will work fine for a person that gives just the small amount of water that I described. Everyone will do things their own way. I'll keep doing what works for me and others can do as they see fit.

Is it some sort of fungal of blight problem? I deep water and allow the surface to dry quite a bit before watering, which is why I'm ruling out over watering.

Has this plant been sitting outside? if not then the odds of it having a fungal or bacterial disease of some sort is practically non-existent.

I deep water and allow the surface to dry quite a bit before watering, which is why I'm ruling out over watering.

That is your choice of course but surface drying is not a valid indication of the need for water. Stick your finger knuckle deep into the soil.

Over-watering is the singular most common cause of problems with young seedlings hands down. Nothing else even comes close. And fading/yellowing of the leaves is a classic symptom.

No one ever thinks they are over-watering yet as soon as they force themselves to cut back on the watering (not to mention the over-feeding) the plants improve. You have nothing to lose and much to gain by at least trying it.

Good luck.

Dave

I would agree that the effects are probably due to overwatering. Even when the top is dry, the lower parts will still be rather wet. Since you say that you are "deep watering," it's almost a certainty.

A little seedling like that just doesn't need much water. It also doesn't need any fertilizer so you that could be part of the problem as well.

When you water, just aim for giving it enough to stay alive and nothing more.

The plant looks fairly OK to me. Looks like it could be some blight. I'd clip off the damaged leaves and reduce the watering as recommended.

I've never seen blight on a seedling.

Thanks everyone! I'll stop worrying and start watering less.

Potting mix that holds too much water is like fighting a losing battle. Peat and perlite wouldn't have much in it for the plant and your kelp fertilizer by your description seems unbalanced.

I think a good potting mix with some extra perlite in it might have the proper pH and a little fertility. I am no expert but I have found that drainage is critical. I think you have a combination of potting mix holding too much water and a lack of nutrients.

You have a control because your plant with worm castings looks better. Do you have any more worm castings? I am thinking you could put them in water and strain it then use the 'castings' tea next time your plant is dry.

I am having a problem with some of my plants and the difference is I ran out of one batch of potting mix and used another on the later plants. I treated them the same but the earliest potting mix drained well and those plants look better.