Drywall Ceilings Water Damage
The ceiling damage in the picture above was caused from a
hole in the Fiberglas bathtub
problem with the shower pan.
I would imagine that one of these water leaks could have done the damage
to the ceiling by itself.
Whenever you have a water leak on a flat or level area, the water tends to spread out, looking for something with a slope, crevice or gap in it, as it searches for the easiest path away from the leak. In a situation like this, the water easily found the gaps between the drywall pieces.
These crevices in between the drywall, can act like a river on flat land, allowing water to flow easily away from the original water leak. Often these leaks are hard to pinpoint exactly, because water can flow in all directions.
Home Repair Tip: I wouldn't repair the ceiling until the water leak is repaired. The bathtub and shower pan will need to be fixed properly. I would advise you to wait a couple of months to make sure the bath tub and shower pan isn't leaking before you repair the ceiling.
If there is another water leak, at least you have repaired the ceiling, only to repair it again. If you're not interested in waiting, at least remove the damaged drywall to expose the area underneath the bath tub and shower for a few days, while testing to make sure there aren't any leaks.