Actually quite a few years as LL(blush), but other tenants are n

1,不续就不续,又不是求他.

    You are right. They are troublemaker. Told them to move out by the lease end if not satisfied with the solution (they replace the filter, we cacuum clean the vents)

2,有狗不说能罚款吗?看看当初怎么写的? Tried not to upset them in case they make more mess before the moveout.

３，应该是他们自己换ｆｉｌｔｅｒ吧？ Yes. Asked them to.

４，他们不换，事后还是你自己清扫一下，但就不给他们做．Yes. Told them will vacuum clean the vent. If still not satisfied, they can move.

Thank you. Will update.