It is normal to produce less milk at night. It is just the ebb and flow of milk making hormones. If you supplement at night it will tell your boobs to produce less milk. Try allowing the baby to cluster nurse and see if the baby is satiated. There is also a 6 week growth spurt and the baby will nurse frequently for a few days for your supply to catch up. Many babies also cluster feed in the evenings, meaning that they nurse frequently in close together spurts.
Liz
Liz