r/BathroomShrooms

Previous owner didn't seal the shower cabin to the wall correctly. Water got under it and under the cracked floor tiles(he messed up the floor too. The whole bathroom was his one big disasterpiece.) The subflooring under the tiles started soaking in the water and expanding, cracking and dislodging tiles throughout the length of the bathroom. The fibreboard subflooring never dried, so black tendrils spread under the whole floor. The subfloor wrecked the tiles under the toilet, which developed a leak between the outlet and wall pipe, allowing much more dookie water to seep under the cracked tiles. This was 3 years ago and we have since ripped out everything down to concrete and re-did the floor properly.

I recently opened my concealed cistern after having had to remove discolorations from my toilet bowl on an almost daily basis for the last couple of months. This greeted me, but there seem to be no similar pictures anywhere and I just can't figure out, whether this is mold or anything unhealthy in general.
Anyone seen something like this before and able to tell me what this is? My landlord insists this pollution is normal, but I don't quite believe them yet, since I've had trouble breathing for a while and it disappeared, once I had removed these blobs...