Welcome to the forums.
Your issues are common to indoor outdoor growers like myself and are predictable with the seasonal changes we place on these tropical plants.
Always remember bananas are tropical and do best and thrive in a tropical enviroment bringing them indoors is still not a tropical environment.
Your plants are classic examples of being indoors 7 months for the winter.....mine do the same thing.
You will observe that a smaller plant is easier to manage than a larger taller plant indoors
Spider mites.....I get them too.
Do a forum search and read some past threads on how members have chosen to control them.
An internet search on spider mite control will offer a trove of information too, just pick and choose what might work for you.
Now that you have mites assume they are everywhere, treat everything containers, saucers, soils, surrounding areas and all plants . I have observed mites traveling nose to tail(just like ants) along a railing to get to another host plant a many meters away.