2 month old feedings

How many ounces do/did your 8 week old take? He was regularly taking 4 ounces every 3 hours during the day & 4 hours at night (8 feedings total per day, pediatrician approved), but now that we’ve switched formulas due to tummy issues he’s only taking 3.5 and at night I’m lucky if I get him to take 3. His weight is great but everything I see on google says 2 month olds should be taking 4-5 ounces every feeding, I just don’t want to underfeed him. Thanks:)