Anyone's babies milk intake dropped without weaning?

Ra

My son is formula fed. He was taking roughly 30-35oz formula daily. He will be 5 months on Mon and for well over a week he's just not been interested in his bottles but doesn't act hungry or wake for feeds during night in place of what he's missing during the day. Yesterday he totalled 21oz and today 22oz. Any suggestions? I was going to start introducing solids but don't know if this will wake the problem worse.