My DD is nearly 18 months, also very tall (97th percentile) and only half a shoe size bigger than your DD.

She is a bit clumsy too, but that's because she was born with a torticollis that hasn't been completely resolved so she is having some sessions with a paediatric physio at the moment - we have been given some exercises to do at home to help straighten her out (literally!) and at this age they respond so quickly.

Check out your DD's feet when she's walking around and standing still - see if her feet are straight or turned in. My DD's stood with her feet straight but her toes angled inward, particularly on the left foot and that was the foot she always tripped over with - the same side as her torticollis. She probably has it because she was a big bub (4.27kg) and was running out of room in utero.

If you think there is anything unusual about the positioning of your DD's feet, it might not hurt to just get her assessed by paediatric physio (not a normal physio, one who specialises in kids). I am lucky enough to have a stepmother who is a podiatrist and she steered me in the right direction.