Kinda odd

Today my little girl went for her 6 month check up and the weighed her and measured her her weight was great 17 lbs and her length well it caught me by surprise .. she usually has a steady growth of about a inch to a inch and a half every mother since birth well today the measured her and she was 26.25 inches but she was also 26.26 inches at 4 months she went from 97 percentile to 50 percentile ... which meant she did not grow at all ... I was concerned but her doctor showed no concern ... any body have this happen with their child