Formula store brand vs name brand

My daughter was put on Alimentum at 5 weeks old due to a CMPA. It’s been working great for her. Fast forward to almost 15 weeks old now and there is a shortage. I can’t find it anywhere. It goes through my insurance and even the pharmacy can’t get it from the wholesaler. The guy at the pharmacy said they have a store brand that is similar so I picked up a can and I spoke to the pediatrician who gave the ok to try it, but now she’s projectile vomiting every feeding. I’m wondering if there is something in this formula that is different than the Alimentum. Anyone else have issues with Walgreens brand hypoallergenic formula and vomiting. Baby is fine otherwise. Still has her normal bowel movements. Isn’t crying or fussy. Just hungrier more because she throwing up more. I was able to find a target across the river from me who had a few cans of Alimentum so I snatched them up in the mean time. Should I toss the rest of the can of the Walgreens brand?