It seems that what I thought was nutrient shortages is actually spider mites. This is a bad infestation and I have a history of not being able to deal with them. I need help. How do I kill these things without killing my plants?
What kind of plant is it?
ladybugs, predator mites, other garden spiders, preying mantis..
or you could use soapy water, or a professional insecticidal soap
they can be dealt with, but if the infestation is bad, it may be too late for the plants, but it certainly can't hurt to try