J.J.
My little one is 8 1/2 months old and she started waking up frequently a couple weeks back. I was so frustrated and concerned. Then about a week or so of that, she had two new teeth poke through and she's now back to one night waking, per night. I don't know of any other reason than what you listed, but I know that it will pass. It's so frustrating at the time, but soon enough she will get back to a routine. Good luck!