I use both Chicco and Nuk. It seems that it's not because of the problem of individual brand. You may try to check if the hole is too large or you didn't screw the bottle tight enough.
真係唔講唔知NUK仲有分SMALL/MEDIUM/LARGE奶咀,以為佢得1/2/3分jar...我阿B(四個月)依家用緊1號奶咀,其實應該base on what來決定轉2號奶咀呀? 轉之前好唔好試下make the hole bigger or add one more hold in the 奶咀first 呀??? Thanks!!