Baby vomiting after formula

My bub is 12 weeks and breastfeeds but now I am trying to introduce one bottle a day. I bought a pack of SMA RTF 200 ml (6 bottles). I gave him a bottle everyday for 3 days and he was fine then I gave the fourth bottle after 2 weeks and an hours later he puked all of it. He went to sleep right after and was happy afterwards. Then I gave him the last bottle from the pack after a gap of 2 days and he puked after 3 hours. This time the amount was lesser than the last time but his stool was quite runny the next morning.

I thought this was an SMA issue and got Aptamil RTF yesterday. He was refusing the bottle but somehow I managed to give it to him and 40 minutes later he puked at least half of it. He also had runny poop. What should I do?

Something worth noting is I have been giving a bottle or two of pumped everyday from the beginning, but kinda took a break in the past 2 weeks hence introduced RTF formula. He was very happy with the bottle but been refusing it since 2 days (once with SMA once with Aptamil)

Baby seems happy tho. We use mam bottles with 0 size teat