Yes, rubbing alcohol will help. MIX 1 part isopropyl alcohol, with 2 parts water, and a dash of dish soap in a spray bottle. Spray the plants liberally with the solution every day or two days. This should definately impact the mites populations and with some dilligence, will eventually eliminate them. Good for plants, good for people!

As for the phenotypes, there are definately a million possibilities. There are about a quadrillion factors that can affect genetics, so it would be very hard to pinpoint anything without knowing a complete and definate history of your plants. Anyways, it could be as simple as, no offense, that you are selecting the wrong qualities in the plant.

Just my thoughts