|I have a patio garden 6|
|Most garden vegetables need 10-12 inches of root space, minimum. If your planter is only six inches deep I don't think your plants will grow well. The yellowing leaves might indicate root stress or possibly overwatering. I'd transplant them into deeper containers to try to salvage them. Some shallow rooted plants include leaf lettuces and radishes. You might even get peas to grow in shallow soil.
Worms love collards, cabbage and Swiss Chard leaves. You can pick them off your plants or you can use the botanical Bt (bacillus thuringensis) to control them. It is sold as Dipel in the garden centers. Be sure to apply according to label directions.