Thanks for the update. He's probably on prednisolone because this is what my Starr is also on. If the food that he's eating is darker in color then this is why his stools are looking darker. If not then you should mention this color change to your vet.

The pred will make him very hungry and thirsty so don't be alarmed about this. He may also start sneezing or having the sniffles at first because this is how my Starr has reacted each time he's been back on the pred. With Starr it went away in about 1 week. Unfortunately the pred makes their immune systems a bit weaker.

I sure hope that Ollie will do well on his meds and new diet and will start gaining some weight back and forming firmer stools. I'm still having some issues with my Starr and I most likely always will. Please continue to keep us updated. Good luck.

You can also crush the pred into his wet food and he shouldn't be able to taste it so this can be another option for you.