4 month old stopped eating,

Me

My son will be 4 months in 3 days.

On good days, he eats 3-5 ounces a feeding. The paat week or so that’s gone down to 2-3 ounces every 3 hours.

Today he ate 2 oz at 7:30 then refused to eat until 2:30 when he ate 4.5 oz. around 2 hours later he ate another 2 oz, and then 4 hours after that he just ate another 2.

So all in all, in the last 13 hours he’s only eaten less than 9 ounces. When he really usually eats 16 in a day...

We formula feed, use avent bottles and have since his first day. We recently switched him to sz 3 nipples and he’s done great on them.

Any idea why his eating has gone down lately?