My 8 month old is on Pro Plan its fab she just loves it
I never feed anything but dog food ..I am mean ..mine never have our food.
My 2 with sensitive tummy have JWB
They do get pedigree white dogs ( low in fat ) biscuits at bedtime and when I leave for work
I would take him off all dog food and feed white fish and rice for 36 hrs then decide on a good dry kibble such as Pro Plan, JWB ,Royal Canin
introduce very slowly whilst on white fish and rice .....I mean over 7 days ish. I see he has tried many foods for his tummy in a short time this may possibly be the problem.
Have you tried a little live yogurt to stablize his tummy when its upset ?
Jo