I'm new to YT but wanted to reply to your post. My first yorkie, Katie, was diagnosed with the same thing when she was about a year old. Her vet put her on Flagyl for a few days and each time we took her off of it, it kept returning so he kept her on it for about a year. I finally found a wet food her system could handle (Pedigree in the small square container) and she was able to come off the meds. It broke my heart each time it "flared up" on her but was relieved when it disappeared. She remained "colitis free" until her sudden passing at the age of 9. The two I have now have shown no signs of it so I'm thankful for that. Hang in there, your baby will be better soon
Suzi