bumps

Hi, I can't seem to figure out what's happened from Googling/forums. Does anyone know why a skim coat is producing tiny pimple-like lumps in various areas across different walls? Skim coat on top pva coated plastered walls. Photos show an almost dry wall (harsh torch angle to show details) and...

What has happened here? I also have tiger stripes in other areas, lots of areas that look lumpy - never seen in any other house.