On my bathroom ceiling, the paint started to peel away in a longish area that's about 1 foot x 6 inches. I scraped off the paint and repainted and it still peeled. I've also trying putting some drywall compound on it and now that too is powdering and not sticking. The thing is there is another bathroom with a toilet which is directly above this one on the floor above. So is this water damage? Is there an easy way to find out? The patch is not obviously wet to the touch. Thanks for any help!