Poo consistency on wet food-Arnold still seems off

I took Arnold in 2 wks ago for a bloody stool. They gave him meds that we were unable to get in him. He'd puke right after giving it to him or he just wouldn't touch whatever we tried to hide it in. He seemed to be getting better, but now I'm wondering as it seems to come and go. Today it was really smelly again and loose, some mucous. Could it be something he's eating? I can imagine an all wet diet would cause looser stools, but not bloody or mucousy of course. For my kids, mucous and blood is a food intolerance issue, could it be for a cat too? Are there common things cats don't tolerate well?