What did the doctor say Edith had on the St. Patrick's Day episode? And she was afraid to tell Archie because it would ruin things or something like that.

to not do anything and Archie wanted Edith to cook.

Edith had something called Phlebitis in her leg. It's a blood clot and it can travel and kill you if you don't stay off your feet. The doctor ordered her not to cook the meal, but being the kind-hearted person that she was, she cooked it all. She did not want to ruin Archie's plans, so she kept her illness a secret for awhile. When Archie found out, he'd wished she would've said something.
-Kristi

I think that was the last "AITF" episode, then it became "Archie Bunkers place"