What causes the base of the stems of tomato seedlings to wither (shrivel up)? I've noticed this happen occasionally. The remainder of the plant is fine until it dies from being separated from the ground. It seems like it happens more often when there's less light, but I could be imagining that. This affects at least seedlings that are still on their first or second leaves. I haven't seen it affect anything but seedlings.
This didn't used to happen. So, I'm thinking it might be a pathogen, or something to do with the soil.