puppy with runny poops

Hi all -been a long time since I was on here-now have a 3mo old male dk apricot Standard Poodle called Brick-was born 5/10/18 and we picked him up 7/7 from the breeder-she was feeding the litter Wellness grain free puppy 3x/day amts according to package recommendations-all started ok then he had solid poop in the morning and as the day went on it turned mushy/pudding like-took him to my vet on 7/9 and wormed him and put him on Flagyl for 10 days-now we are back to the beginning-Vet recommended rice with food so we r doing that -I've also started giving him pumpkin puree and yogurt frozen treats(make them myself) today and not too much improvement-am calling vet in am for appt-appetite is good and water intake good-was wondering if protein content of food is too rich for him 32% and is his tummy too sensitive
It has been 9 years since we had a puppy in the house so it's like starting all over again! LOL-any advice is greatly appreciated-
PS- he is walked on a leash at all times so doesn't have a chance to get into bad things or our other dog's poop(14yo lab mix)