Yes most definitely. If you aren't getting enough water it lowers supply for sure. There are many herbs out there that can boost supply and some can decrease it too. If you are not eating enough calories that can lower supply also.
yes it does matter what eat and drink cuz it still goes straight to the baby.Some spicy food make give your baby an upset stomach or certain things you drink can affect the baby to.Just keep the same diet you were on when you were pregnant