Growth spurt?

Can a growth spurt cause baby to want to eat less? He turned 6 month on 1/25. He is formula fed and had been eating about 30oz before that. Around then it changed to 25-30oz per day and his dr didn’t seem concerned but the last few days it’s been more like 20-25oz. He normally eats 5oz at each feeding. Today so far he did 4oz and then 3oz. Is this normal? I’m a ftm and have no idea what to expect at growth spurts or if he’s even going through one. 😩