Cat diarrhoea

[Doggotired]

Hi,
My cat has had persistent on and off diarrhoea since we have had him, around 8 months now. When we got him he was wormed and is regularly wormed. The vet put him on royal canin sensitive food and that seemed to help so I have kept him on it and the majority of the time he’s fine. If he eats anything else he gets a bad stomach so that’s literally all he has.
He has had runny stinky poos since Sunday now, he’s had nothing else to eat but his food (as far as I know) so if he isn’t back to normal I will take him the vets tomorrow but I was just wondering if anyone has had a cat like this who just gets it randomly for no apparent reason? You know like ibs in cats? Is that a thing? He was treated for Gardia when we first got him as a precaution but the vet didn’t think it was that....
he doesn’t go out (his choice) so he’s not eating anything dodgy out and about or picking up bugs from other cats. He is perfectly healthy in every other way and playful, happy and annoying 😂
He was dumped outside a vets when he was 6 weeks old so I’m wondering if he wasn’t fed properly in the beginning and that’s messed up his guts?

Coronavirus cat variety, my cat has had it chronically for years.

Really?! How do they diagnose that? Can you do anything for it?

Yes my cat had this for over a year on and off when i first got her as a foster cat. There was no reason for it that the vet found other than a generally sensitive tum.
Royal Canin Digestive Care dry food was literally a lifesaver!
And then I also give her a tiny amount of very posh real meat or fish food as a treat.

Do you think it’s worth taking him the vets? Last time she said she would do a poo sample but that generally they don’t tell them much but then it cleared up before I could get 3 samples so we never bothered.
I don’t know if he just has a sensitive stomach, I can’t imagine if someone dumped him outside a vets they made sure he had a good diet first....

Yes if he's had runny poo since Sunday the vet might be a good idea. Mine was given some steroids for bad bouts if I remember correctly. And he might also need some nutritional green paste that's supposed to settle the stomach (I forget what it's called though). Also trying giving him some boiled chicken and rice. When you boil the chicken keep hold of the water, they love it and he could probably do with some extra hydration.
Good luck!