Sorry, I saw bedroom and read bathroom; must be dislexicia 
Notwithstanding, the problem is still with the common property and the O/C is responsible for correcting the fault and any damage it caused by it.
So whilst my advice is the same, there’s are opinions (that I don’t share) that any repainting arising from such faults is Lot Owners’ responsibility, the onus is upon you to prove that the faulty drainage (down pipe) gave rise to the damage that you repaired, and that the cost of that was reasonable.
It will do no harm to take the matter to mediation if your O/C and you can’t reach an agreed outcome or perhaps a compromise.