Spider mites!!!!

[Clawhammer]

I have about 35 catasetinae, all in my indoor greenhouse (a bedroom). At the very end of last season, when about 25% of them still had leaves I had a spider mite outbreak. Being late in the season I simply removed all leaves, drenched with alcohol, and repotted. I haven't seen any since and all are in varying degrees of new growth, some quite large.

Except for one plant... Two weeks ago I detected some brown spots that looked a little like spider mite damage, I drenched with alcohol and moved it to the cattleya section to keep it away from my other soft leafed orchids. I watched it like a hawk for the last two weeks and didn't see anything. This morning I saw one.

I now have that plant on a separate floor. My other catasetinae still look pristine.

a. How to best treat the affected plant?
b. Preventative treatment for the others?

Thanks in advance!