Avocaods and mushrooms contain polyols and sweet corn contains GOS which are considered FODMAP unfriendly. Bell pepper are consider FODMAP friendly. Also, corn is high in insoluble fiber so it can be a problem. Check the tables in the first two links in my signature for a list of FODMAP friendly and unfriendly foods. Also, here is table of that may be helpful too.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS
While soy is off limits they have found that the way tofu is made from soy beans is safe. Apparently the unfriendly ingredients are removed during the process of making tofu from soy.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS