Maybe growth spurt?

My 6 week old has started not eating as much and sleeping a lot more. He went from eating 3-4 ounces at a time to maybe 1-2 ounces now at a time. He sleeps a lot more too so he isn’t eating as often. He has cut his intake in half! It’s making me nervous but he is having wet and poopy diapers still so he isn’t dehydrated. Is he going through a growth spurt and should I let him sleep or should I be concerned about that fact that he isn’t eating very well anymore. Formula fed baby.