Did the vet check for coccidia and giardia?
How about trying Hill's w/d food?  This has helped some shelter cats with
runny poop.

First, have a complete evaluation by your vet to make sure nothing of a
medical nature has been missed.

Second, Gerber's baby food is fine as an occasional treat; but it does not
have the correct nutrition for a cat.  That may actually have been
contributing to your cat's diarrhea.

Third, I had a cat with IBD who had continuous (and intense) bouts of
diarrhea.  Imodium AD turned out to be the best medication for her.  The vet
showed me how to whittle the pill down to the right size (it was about the
size of a BB).  Make sure it is regular Imodium AD, not the chewable type
and not the advanced type with other additives.  Also check with your vet
first to make sure it is approved.

Finally, a good-quality canned food will be much better for your cat.  It is
common for a cat that is used to dry food to reject canned food, but it
*can* be done.  Google this group or post a question if you want
suggestions.

MaryL