I just bought these bottles and was told I should return them and get Avent bottles or a different brand because the nipple kept collapsing when she used it for her babies. Have any of you mommas used this brand before? How did they work for your babies? PLEASEEEE let me know. A lot of time I ask a question on here it goes un-answered. But I would really appreciate input so I know if I should return these and get a different brand for my baby (she's due in a month) TIA! :)