Hi @sred,
It's difficult to say because the photo doesn't give a huge amount of context. Is it possible to get a couple more photos, maybe one from further back and one with a light shining on the patch?
It doesn't scream water damage to me, but it is certainly possible. Does the plasterboard around this area feel damp? Does the plasterboard feel softer than in other areas? Are these patches bubbling?
If any of these symptoms are present, then it could be a water leak, in which case, you would want to solve the moisture issue before repairing anything. If there is a leak in the ceiling, then you'd want to have a leak detection specialist check it out for you.
The other option, which I suspect, due to the uniform size and shape of the damage, is that the installer of the plasterboard missed the stud with their screws, so they kept driving in a whole lot of screws looking for the stud. It's poor practice, but trust me, it happens. If screws don't hit a stud, then they will, over time, sink through the plaster and paint, revealing themselves as little circular shapes. If you use a 100mm Sharp Edge Paint Scraper to take the surface of these bumps off, if this is correct, you will see screwheads.
If you find screwheads, you will just remove all these screws as they aren't going into any timber and patch the holes with a small amount of Multi-Purpose Joint Compound before sanding, priming and painting.
If we can confirm it is water damage, after having the source of the water handled, you would cut out the affected plasterboard using a utility knife, ensuring you wear gloves to protect from lacerations, then either use a Plasterboard Patch, or install a Plaster Repair Panel, then plaster, sand, prime and paint.
Check out How To Patch A Plaster Wall and How To Repair A Large Hole In Plasterboard for some guidance.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
