Re: advice wanted - slow weight gain
90th percentile to 50th doesn't seem that bad; I think you and your ARNP are being wise to not freak out. My LO went from 50th at birth to 9th at one point. Even then, our pediatrician just encouraged more feeds, etc rather than sounding alarms. Overall, our pedi thought my son looked great, was meeting milestones, was bright and interactive -- all the stuff you describe about your LO.
I would think about more frequent weights, and I was TOTALLY freaking out when it was my son who was dropping, but with a lot of reassurance from the pediatrician, I look back at myself and laugh.
DS Ethan 12/16/2008
Breast fed/pumped 11 months as a surgical resident, 80 hours a week at work
DS Abram Daniel 12/20/2012
Feel like we've gotten a strong start