You're welcome
I mostly use Pure Bites personally,as it is the easiest brand to find.Petco,Petsmart,etc carry it,in fact Petco often do sales at least on the cat sized bags making it even better!Some other brands may be available in local specialty dog and cat stores,but the main idea is something not irradiated from a reputable company that is pure meat.Pure Bites also do shrimp by the way which could be used as a rotational protein source.
Getting off antibiotics should help.Hopefully things get better soon for the little guy,even if just a tiny bit!