It is too hot for them. They should not go over 82 as it causes them to overheat. Also have you been changing the water regularly in the bowl? It looks very small and I would say would need to be having twice daily changes of at least half of its water. Ammonia builds up very fast in those little bowls. He could be getting poisoned with his own wastes in that sized container and no filter.

I am afraid for him in that bowl without the water changes and he really does need those peas as they are like a laxative to bettas. Sorry to be so insistent but he looks really sick.

Rose