What jimscott said.
Dribble slightly lukewarm water on affected parts. The coating rinses of easily enough with lukewarm water. Repeat as needed. Without the coating the leaves grow normally. Then just flush your media with top watering. Discard the runoff. This is only a temporary problem that varies depending on your batch of peat moss and how well you rinsed it. It eventually clears up as the compounds responsible get flushed out of the medium.