Just to give the other side though... DS did not grow an inch or gain an ounce from his 1st to his 2nd birthday. He went from high percentiles to very low.
But, in that year, his *mental* development grew by leaps and bounds, much more than the "average". So by age 2, he was mentally about 2.5-3yr equivalent, though pretty small physically.
Since then he's been "catching up" and stays at just under the 50th percentile on height -- he's almost 10yo now -- and is still "gifted".
So I really think he was just putting the calories into his brain rather than his body.
It's certainly worth checking into celiac and other disorders, but if she doesn't seem to have any other "symptoms" honestly she might just be in a "plateau" growth stage and growing other parts of her insides, like her brain.
DD seems to be following a similar curve... she grew lots until 10mo and has barely gained at all since then, she's now 14.5mo. DH and I are both very tall and she has the tall "look" to her but right now she's only 50th percentile-ish -- 22lbs and 30". We're not worried at all.