Hi all, We've recently moved into one of our IPs with the goal of slowly renoing while we're here. I've discovered what seems to be water damage in my son's bedroom which backs onto the bathroom. As you can see from the picture the paint is bubbling and the plaster can be scraped/rubbed away with your finger. The house is double brick so I'm wondering a) Is it serious? And b) is there an easy fix? We'd rather not rip out the entire shower just yet.