Margaret had her six month checkup last Friday. Among other things, the doctor mentioned that her growth rate was slowing down, but assured us that was normal for breast fed babies. I suspect it's especially normal for breast fed babies who have recently been through an ear infection.
I was curious about the specific measurements, so I've now compared them to the CDC graphs. Between four months and six months, Margaret's height/length has dropped from about 70th percentile to 50th percentile; her weight has dropped from about 45th to about 30th. Both of these figures have increased in absolute terms, but are "falling behind the curve" a bit.
Her head circumference, however, has gone up from about 50th percentile to about 65th. Perhaps that's what one would expect from using human milk instead of formula based on cow's milk.