Oh dear, contaminants!
I had a similar issue with VERY itchy fish due to either hair spray or oldspice, one of the two was somehow able to get a tiny amount into my tank despite both a good lid and fair distance. Lesson learned, do not use aerosols of any sort in the same room as your tank, even if you're careful with them.
Isn't pledge that wood-polish surface-cleaning stuff? I seem to recall my brothers and I using it on our toboggans to make them slippier on snow hills. ...and that one time my brother sprayed his sock and accidentally made deadly frictionless spots on the staircase. If it's the same stuff - YES IT GETS EVERYWHERE I would totally believe it a plausible cause.