Our horse performed wonderfully all summer.
then we took him to a 3 day show, less than 1/2hour trailer,only on 4 or 5 times, both eq and 2ft jumper. well rated. home from show COLIC, first time. Vet came blood work fecal sample, exam. She thought maybe dehydration, gave IV fluids. Put on pepcid for possible ulcer. We rest him for 6 weeks. Then put saddle on and short ride on flat. ??Colic again, Vet came..not as bad as last time, maynot really be colic. He stretches, and paws, no sweating, no rolling. Now planning on resting again for a few months, pasture and barn (with other horses, no recent changes) Any ideas what this is? After his first colic he had a sensitive back for a week.

May not be related-first thing that came to mind;
Kidney's

I agree with possible kidney issue, due to the sore back!