Can I ume this is a growth spurt?

My daughter is 15 weeks old, going in 16 weeks. She has been a great baby as far as sleeping goes - she sleeps normally from 8 or 8:30 until 6 or 6:30 in the morning with no midnight wakings. The past 3 nights in a row, she has woken up and needed to be fed. I tried to hold her off by giving her a pacifier, but I knew she was starving, so I ended up feeding her. I'm always concerned about something becoming "habit" but then I thought maybe she is going through a growth spurt. She seems to be taking 2 extra bottles a day. I don't know if I need to increase her ounces during the day (she is at 6 ounces per feeding every 3-4 hours during the day) or if it is just a growth spurt. Any ideas?