Maybe the problem is that modern infants are getting fatter!
http://health.msn.com/pregnancykids/articlepage.aspx?cp-documentid=100142529>1=8404
It doesn't seem surprising to me that your child would grow at a slower rate
than babies fed the SAD foods. It's like a calf eating natural pasture and
mother's milk compared to a calf force-fed corn and ballooning to an
enormous size quite quickly.
-Elizabeth