I went to my job today to lay carpet tile out, and notice one wall where the joints flashed a light yellowish line, the size of a tape from top to bottom. 4 lines on the entire wall, which where 4 joint. All stand-ups. Land-lord finished these walls a year ago. They where meshed taped. I primed with Sherman Willaims Pro Block and painting the wall a white color, egg shell finish. After 2 coats of paint on the walls, I was done. However, today we notice the yellow lines, the size of a piece of tape running from the top of the wall to the bottom. Could it be some water got behind the wall and caused this to happened. The area has had the AC running all the time, but no other walls have this problem. I checked above the acoustical tile for a leak, but everythign checked out good. Weird. I'm going to have to hit it with some killz.