I recently purchased a condo that was painted sea foam green by the previous owners. Can't stand it! The place was built in 1978 so I expected a few issues but not a huge section of wall! So I started sanding with an Orbital sander. Everything went fine though, on one wall, I noticed the wall texture was different from the surrounding area and there were small pores in the paint surface. After wiping this section down with water that paint started blistering. Moisture issue. Not a big deal I had this issue when I painted the bathrooms a few months earlier - expected it. I put the sander on it again. Paint came flinging off but not to expose sheetrock but a fine off white surface that turned to powder when I put the sander to it. What is this? Mud? What is the proper way to fix it? My fear is the majority of the back wall is like this! I am starting to miss the sea foam green! I've attached a few photos and any help would be appreciated. I want to make sure I do this right so the next owners don't have to go through this too. Also, ignore the little white section. In addition, you'll notice it's framed between two sections of sheetrock. There is also a small section that is red. Really bizarre!