My LO is 3 months old. She used to feed 5oz of formula every feed 5 times a day. Lately, she's only been taking 2-3oz with some feeds. Her cousin who's a month older is going through the same thing. Is this a normal phase that babies go through? I weighed her a few days ago, and she's at a healthy weight of 12lbs 12oz and is otherwise happy and content - should I be worried?