I've got several hundred annuals, perennials and tomatoes started well under lights. Many are now 4" or higher, and they are all in pots about 3 inches square.

I've been fertilizing them with a VERY weak 10-52-10 every week or so,and most are looking fine. However, a few dahlias have some yellowish bottom leaves.

Would that indicate a need for a different fertilizer...or might it be the small pot size?

Knowing it's probably four weeks before these can go into containers or beds, is it a good idea to repot them into larger pots?

How do others handle this?