If a kitchen wallpaper i painted little more than a year ago is brittle and cracking, what might i own...? ...done wrong? might it be a case of using the wrong type of...

...done wrong?

might it be a case of using the wrong type of paint for the kitchen [whats the right type]....
or is it that the stratum i painted on top, has somehow react with the wallpaper underneath and cause it to crack?

the same is scheduled to artex near a windowpane, that i painted over...the artex is starting to crack &crumble in places.
Answers:    I agree near GER - its down to damp and condensation from cooking.
its moisture