Rental situation: being told we have to pay plumbers invoice for hair clog

Our property manager sent a message saying hair clogged the tub/sink drain in the bathroom, that it's "not normal use," and that the housemates need to split the plumber's invoice of $250 basically accusing us of cutting our hair in the shower.

Some context: the plumber was originally called for a clogged toilet, but I actually fixed that myself the night before. The plumber still came the next day anyway, so since they were already there, we had them check the tub/sink too since the drainage had been slow for months. That's when the hair clog got mentioned; not as its own separate issue, but as an add-on while they were already on site.

What I don’t understand is why we have have the pay the invoice when hair going down a drain over months of use is normal. Like people wash their hair and it sheds, bodies are shaved.. it’s inevitable. This house has had ongoing maintenance issues in general, and there's no telling when the pipes were last actually checked or cleaned before we moved in. Also other tenants lived here before us, so any buildup isn't necessarily even from us.

I personally am not on the contract of the house as I’m subletting the room that I share the bathroom with one other person. It’s a big house and there’s 2 other bathrooms.

Just want to know if anyone has ever dealt with something similar to this before. did you push back, and how did it go? Right now they are threatening to report us if we don’t pay. Are we obliged to report also..