I agree with Keriann. Yes, you should really let them dry out. Matter of fact, once my seedlings are as big as yours, I let them dry out pretty much all the way before I water again. You can tell they need watered when you pick up the flat and it feels light as a feather. Then after you water, it's much heavier. Your method of bottom watering is quite unique, I must say. I think that most folks bottom water the way I do, which is to say setting the cells or cups into a tray of water and letting the plant absorb as much as it wants until you see moisture on the surface of the soil (usually takes anywhere from 5-20 min). Now, I can't say for sure what positive or negative effects your method of watering might have, except that it sure sounds like a pain in the hiney to me, and I somehow doubt that the soil is getting properly saturated. You want to simulate mother nature; a soaking rain. Then you want to let the soil dry out. That's how it is in nature. Roots need water yes, because the plant needs water, but then they need to dry out and get oxygen. Damp soil all the time = no oxygen to the roots. Now, I can't say for certain what part of your program is causing your issues, but I would start bottom watering them as described by letting them absorb water sitting in a tray. I think you will find that using this method, you should only have to water every 3-4 days, or less. I would lay off the ferts for a while, and then make sure only to fertilize when the soil is already damp, or you will burn the roots. I just mix the fert with water, then pour into a tray and bottom water as usual. Give this a shot, see if that doesn't help.

I had a soil test done and the nutrient levels are very low, as is the PH. This is my first garden, so now I know I need to lime and fertilize. According to the link you provided, that seems like the most likely cause of the YSD. Its the end of the growing season, so I'll be disposing of the plants for the Powdery Mildew. Thanks!

Yeah I'm in Canada so it's not late in the growing season for us. ;) This might actually be a blessing in diguise since when I went to get more seedlings I decided to branch out, variety-wise. So now I've added another tomato growing location and am experimenting with Sweet 100, Sweet Million, Ultra Girl and Better Boy. I know they may seem like a bunch of boring old hybrids to you tomato veterans but it's plenty of adventure for a novice like me. Thanks for the help folks and I'll be sure to keep you posted on my progress (threat or promise??). Love this forum.

I'm using a regular "universal" soil (it's really poorly described on the declaration), nothing added. Seemed to work last year well so I didn't think any chance is necessary this year either. No drain holes as I tried to water just enough to wet the soil and not drown it. This might be a problem if I wasn't careful enough and did over water some of them. As stated above, I try to wet the soil and then re-water when it gets almost completely dry.