Ive had a shower leak for a while it seems and it looks like it is due to cracks in the grout. I noticed the bottom row of tiles some were loose if i pushed them. I removed the problem ones with a view to replacing but the plasterboard is slightly crumbly. Is there any way to prep it before putting the tiles back? Also should i silicone the bottom round the tray with anything special? I would raplace the lot but i cant get the tiles anymore and the tiles are in entire bathroom. I did think about one of those acrylic panels instead.