Decrease in appetite?

Anyone else's 6 or 7 month old have a change in the amount they eat? My baby will sometimes act really hungry but then only drinks half the amount he usually did and push the bottle away or just act the least bit interested in eating and everything else is more important than his milk. He used to LOVE his milk but as he's gotten older, could care less. He always drank 8oz no problem but I'm lucky if he drinks 5-6oz now. Usually 3-4oz and he's done. I haven't changed his formula either. Is this a normal thing in older infants? He is completely healthy otherwise I'm just starting to wonder about this change in appetite now.