The only well-documented effect of diet on pouchitis is that for some people carbohydrates (starches and sugars) may increase the frequency of pouchitis. Bacterial probiotics can also influence (decrease) the incidence of pouchitis, but most people get the necessary doses of those from supplements rather than diet.

Have you tried Flagyl?

I don't think diet, yours anyway contributed, unless you had not been eating fish before? Then you don't have as good a reference point as the fish could be an issue. I however have more issues with veggies and no issues with meat for diet and pouchitis. I have always been put on flagyl and Cipro together and gotten good results. I also take visbiome packets of probiotics and that usually keeps pouchitis away. If I feel like I am starting to get pouchitis, or I'm just feeling off in my gut I take a second dose for a couple days and I can not need the antibiotics.

Good luck