Hi all... I have beautiful mid century concrete floors we stained with ferrous sulfate and then put 2 coats of commercial grade high gloss polyurethane. We did this about 2 years ago and don't wear shoes indoors. Over the past 6 months, I've noticed a very dulled finish on the high traffic areas - I figured it was from oils and also from where the dogs run around. No, scratches mind you, just a blurry dulled look only on high traffic area. The other areas shine like crazy. I have tried ammonia mix as it was suggested online and even a test spot with rubbing compound thinking there was a film that the compound would quickly take off. No luck!! Any idea what the buildup or reason can be, and most importantly how to bring back the shine? After 2 years of high quality commercial grade poly, I know it's not time to sand and apply again! Thanks! Sylvia