I have seven month old twins that have mspi. It took a LONG time to figure out with basically no help from the ped or the GI dr. They didn't really have very typically symptoms...basically a LOT of screaming and very infrequent green mucous poop. It seems to be under control now with the elimination of dairy and soy from my diet (they are finally happy and seldom scream). poop is still not right, but the GI Dr said they'll grow oy of it and it Wilson improve once we start solids. Meanwhile, one of the twins is not gaining weight well at all. They want me to supplement a bottle a day with rice thickened nutramigen and she hates it and won't drink it. The other one is gaining okay though, so I don't think it is supply. I did a weighted feedbg this morning and she took in 5 oz. I wonder if she is still being exposed to the bad proteins and it is causing damage somehow, and if so if I should eliminate more from my diet. I don't know what the next logical step.is. basically the doctors have mostly proven to be useless, so I feel.like I am on my own. They also have reflux and are on zantac for it (the ped GI didn't want to switch to a PPI as he didn't fill the benefitsnwoukd outweigh the risks. Did I mention useless? I think their big problem is food intolerance though...and it also scares me to even think about starting solids.
Re: mspi further elimination..?
I'm really late to this post, but I agree that it could be something else in your diet that is upsetting your LO. For my LO I ended up eliminating dairy, soy, eggs, nuts and tomatoes (too acidic for him). But it was a struggle to figure that out, I ended up on a total elimination diet. You could try an elimination diet, or you could start smaller and eliminating some or all of the other top 8 allergens (dairy,soy, peanuts, tree nuts, wheat, eggs, shellfish, fish).
Here is some info that was extremely helpful to me when I first started elimination foods:
https://www.askdrsears.com/topics/feeding-infants-toddlers/food-allergies/elimination-diet
https://kellymom.com/health/baby-health/food-sensitivity/#specificlink
Elimination Diets video: https://bit.ly/yL1gFN
HTH, and hang in there!