KoKo,
Give you one more tips. If you change the cap (i.e the colour one) from NUK to pigeon, it should be more better. For my son, he used NUK bottle + pigeon cap+nipple since he didn't like NUK奶咀, and I tried NUK cap+pigeon 奶咀, the effect was not good, so I tried Pigeon cap +奶咀, it is more better. Try try la, and so for my daughter, all of them are pigeon