Question with warming formula

So i switch back and forth with enfamils gentleease prepared milk and the powder formula. When he was on the prepared formula, I’d have to somewhat warm it up due to having it in fridge. He started to spit it up a little more than often so I said well maybe he’s not liking the prepared milk anymore? So I went to formula he’s been on powder formula for two days and since then he’s been having little diarrhea squirts, he’s been more fussy an isn’t sleeping as much. Can the change of texture in milk have affected him? Should I switch back? I’m thinking I should just wanted some input? He’s almost 6wks.