[mimimomo]

Did you feed him anything other than Hill's I/D?
Dogs w/Colitis (inflammation of the colon or lower intestines) needs to be on a very strict LOW FAT/ HIGH FIBER diet.
I agree w/everyone, he needs to be seen by a vet. Sometimes when a flare up happens, bacterial overgrowth (usually stinky smelly poop indicates bacterial infection) can make things worse if left untreated. A good probiotic added to the strict low fat/ high fiber (preferably not from grains but veggies) diet will keep the stomach's good & bad bacterias balanced, esp if he's been on antibiotics b4.
Stress related problems should also be addressed. No household cleaning products & no pesticides to stress out their sensitive system. No grooming or boarding if they get stressed out being away from home.
My Princess had recurring colitis & she does very well on Honest Kitchen, Weruva (low fat content for canned food, also low in phosphorous) & Canine Caviar.
Hope he'll feel better soon!