Tenant Responsibilities? Or mine?

We own a couple of small buildings – one a 4-family. I manage them, hubby deals with garbage, small repairs, sidewalk shoveling. Usually it’s all good. But sometimes tenants need a repair that I feel is their responsibility — but hubby says it is ours. Interested in the forum’s collective wisdom. This week’s issue: tenants broke a toilet seat, and now their toilet is running as well. I believe it is their responsibility to replace the toilet seat – not necessarily part of ordinary wear and tear. And if they clog the toilet or the tank keeps running, that perhaps they should call a plumber, at their expense, to deal with it. Hubby thinks it is his job. Which ordinarily is okay. But some weeks, like this, he is just too busy with other commitments. I believe the principle should be that it is the tenants’ responsibility and if he can help out, all the better – but if not, it’s their job. They are all well aware that there is no on-site super, and know him. We rent these basic, 4 bedroom apartments at somewhat below market rent. What say you? Thanks in advance.