my LO is almost 4 months and has never had a problem with spit up. We started doing half formula and half breastmilk 3 weeks ago and she did really well with it. In the last week she has been spitting up more than usual. (and its been chunky) I think she has started to teeth.. could this be it? or the formula? She also has just started to roll over, could it be from moving more?

any ideas?