plaster hairline cracks

For a while now I've had cracks in the plaster of the bathroom ceiling and have just started filling them as I'm concerned about moisture affecting the plaster but just today I've noticed new step pattern in the attached picture. Would trying to fill and repaint be enough?

I bought a newly built house nearly 3 years ago, part of a 5 house development. Mine is the first house in a row of the 5 houses and has a back boundary wall and 1 side boundary wall. - The back boundary was a new wall which runs behind all 5 houses, is capped and is not painted. - The side...

Fillered cracks on walls using polyfiller sanded back painted and still see the fillers lines where the cracks were any suggestions guys?