Regression?

My 1.5 year old seems to be having a regression. I just had another baby 2 weeks ago and she is now reverting to not wanting to eat and only drink milk. She's super cranky (I would be too if I was starving myself) but also keeps talking about boo-boos on her knees (there's no booboo). I think she's misidentifying pain as I think her canines are finally trying to push through. I think her teeth hurt but she's confused. Not sure if she's having a regression or a teething issue. Otherwise outside of eating she's still her fiesty little self. Anyone else have babies so close together and see something like this?