Sue,
The setup I have dictates that I keep the grow room door open to help keep the room cool. So I am always introducing new mites. There are times that I am ahead of them but I always have a few. Until I can budget a power upgrade I just have to coexist with the Borg.
I won't go into all the things you can do. However, you brought up removing the leaves.I routinely remove any damaged leaves I find, a few at a time, even if I am spraying. My thinking is, the leaves that have had mites are the most likely to have mites. Another advantage is that the more of the damaged leaves that are removed the easier it is to spot new damage.
canyon