Not certain if the Poster is still around - but I'll add my thoughts/opinions.
I have heard that corn (especially genetically modified) can cause symptoms. I'd stay away from all gmos - for safety.
Have you had any type of blood testing for food sensitivities? Corn, wheat/gluten, soy, eggs/dairy to name a couple offenders?
There may be something in that particular type/brand that doesn't agree with you. Corn and rice should not replace gluten, in my opinion. A varied base of teff, quinoa, millet, potato (if necessary), tapioca, arrowroot, chia...etc., would be most helpful.
Have you tried making your own? I know TIME CONSUMING to say the least. But you can be more selective.
Stick to it. Please. Consumers demanded soft white bread to last on shelves for days...it was not meant to be this way for we aren't eating grains - we were eating chemicals from laboratories to make the breads that way.
Your brain/blood/body doesn't know chemicals. Can't "do" chemicals. I could go on for days about the sad state of our foods and the chemicals in them. But I would be off topic