Dry Lips?

hillek5

So DS has had really dry lips off and on for about 2 weeks or so, and I'm completely confused as to why. 

I was thinking that maybe he's just not getting enough fluids throughout the day--we're transitioning to milk, we're doing formula and I'm nursing (my supply is super low, even with reglan), and DH is a little forgetful about giving him a sippy sometimes.  But, he's also thrown up in the middle of the night 2-3 times in the last week(ish).  He's had a cough off and on, so I was thinking he was coughing so hard he was gagging himself.

All of this is confusing me.  There's too many factors for me to figure out which is the problem.  Do I just call the pedi and see what they say?