What type/size of pots are the tomatoes in?

I find when starting tomatoes and other plants from seed, they do well in a small container up to a point, then they start to decline unless transplanted. Are you growing your plants under lights, or a sunny windowsill? Have they been outside for an hour or two on nice days?

I am by no means a tomato expert but just thinking of a few questions that might help people in determining what's wrong.

Glen