I've been dealing with spider mites on vegetable plants for years, fortunately not yet on my citrus. But you guys seem to be guessing about the spider mites and the effect of the various treatments. By the time you see webbing, you usually have a huge population of spider mites and their eggs. By the time the leaves are all stippled, you have many many spider mites.
Here's an easy way to know exactly if you have spider mites and how many are left after you've soaked yourself trying to wash them off the trees (where do they go when they are washed off, and are the eggs also washed off?):
Try a hand held microscope, somewhere between 10x and 20x. Here are links to the two kinds I've been using for about 5 years. They work really well. The first one isn't anywhere near the advertised 60x, but it gets you close enough to count the eggs, see the really young spider mites, watch them all wiggling their feelers/whiskers/front legs as they suck the life out of the plant. The second one is a little less powerful than the first, but has a larger field of view and is better made.
https://www.amazon.com/Grow-Room-Microscope-Handheld-Magnifier/dp/B01D96ERFU/ref=sr_1_10?crid=33BCDG8EL033Z&keywords=hand+held+microscope+with+light&qid=1569298048&s=gateway&sprefix=hand+held+microscope%2Caps%2C536&sr=8-10https://www.amazon.com/gp/product/B015VGEBS4/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1Myself, I don't use pesticides, so I'm stuck with Safer Soap which kills them dead but you have to be very persistent since the eggs will keep hatching if you don't come back every 3 or 4 days. I'm also experimenting with a handheld vacuum cleaner, trying to find a way to do it without damaging the leaves. Citrus leaves are much tougher than vegetable leaves, so vacuuming might be easier to use on Citrus.