Girls, good day! Could you please tell me, my son switched to artificial…

Girls, good day! Could you please tell me, my son switched to artificial feeding, we buy Nestle 2 formula. Today I opened the package in the morning, gave it to my son, he drank 210 ml, didn't grimace, didn't spit out the bottle. But an hour later he ripped it like a fountain. I tried the mixture on taste, and it had a terrible fishy smell, rotten, mother of God, fish!!! Opened another pack of the same, the formula is excellent, milk-based. Checked by expiry date, both packs until 25 years. What could this be?? ?