MSPI - possible green bean allergy??

my LO was diagnosed with MSPI at 4 weeks old. I eliminated all dairy/soy from my diet while BFing him. I stopped BF him at 5.5 months due to a very low milk supply. 

he has been on solids since 6 months. he had a weird "diaper" rash when eating greens beans and brown rice (earths best jar) for 4 days. the rash is weird b/c it isn't on his butt but more near the ground spreading out onto his inner thighs and is just in that area. he gets freq diaper rashes but this one was just weird and I felt not poop related. now fast forward a few weeks later I gave him earths best green bean casserole (has green beans, wheat flour and onions) I don't think he has had "wheat" before other than a few puffs maybe? unless I am forgetting something? but does fine with oatmeal, rice, barley. well he had the green bean casserole yesterday and again today and now the rash is back! same rash.... he hasn't even pooped today since the rash came about today so I know for certain this time the rash is not from poop irritation. his poop really can irritate him but that goes away quickly. 

I googled and read that NOTE: If your baby is allergic to soy, he may also react to green peas, chickpeas, green beans, lima beans, barley wheat or rye. 

I recall him being fine with peas and barley. he hasn't had chickpeas, lima or rye. I did eat a lot of hummus while nursing and his GI doc constantly said that there was something still in my diet that LO was reacting to even though I didn't eat any dairy or soy. 

any thoughts???? I am going to hold off on any further green beans and wheat for now and the others on the list that he hasn't had yet. I may try peas and barley again, as I feel he has eaten them both numerous times and been ok but now I am wanting to be 100% sure. thanks!