White silky film on my two turtle's legs?

by Cidney
(Texas)

Just the other day I looked closely at my red eared sliders, and they both had a silky looking film flowing from their back legs. I picked them up, and I just picked it off. I was wondering if this is some kind of dangerous infection? Both of their shells are fine; there are no white spots or patches on the shells. But I wanted to know what this white film was?