removed kitchen backsplash to find crumbled plaster

[lydiahams]

I removed a few tiles from the kitchen backsplash with a grout rake and a chisle and hammer to find half the plaster is fine and solid and the other half had a layer of yellow plaster that was very soft. Under the layer of yellow was pink plaster that was very rough and crumbly. It doesn't sound hollow but there was plaster dust all over the floor. I'm not sure what I can do to fix it as I wanted to renovate the kitchen as a present for my mum and now I'm panicked.

Thank you in advance for any advice

 

[Dave]

Morning, its just the skim coat fell off to reveal the base coat ( bonding ). Are you removing all the tiles ?