Been a lurker, but signed up to tell you about my last year's horror of broad mite - and to tell you that I beat them last year with NO pesticide at all and haven't seen a single one since. I even had yields in the end, which was pretty good result considering my mite outbreak had all my plants infested like your pics, and was in July!
All detailed in my obscure blog but probably not allowed to link here so I'll give you the cut-paste (I do hope this is OK). Basically the method is stolen from the folks with african violets who have been fighting these broad mites for a long time, it's a hot water treatment:
- dispose of any badly infested or non crucial plants. Bring the odds in your favour.
- prune all remaining fruit off the plants, edible or otherwise, you want the plant to concentrate on recovery after what you're about to do to it, so remove all the fruits.
- cover the pots WELL with plastic bags. You will be surprised just how much soil can leak out of even a securely bagged up pot, so be prepared for a muddy mess.
- if you have any large plants > 3ft or so, either trim them down or bin those plants, because submersion in entirety is really really important.
- Get yourself some weights. Not concrete or brick, stuff like a few plant trays. But make sure you have sterilised it first if you think there might be mites on it - boiling water would work I guess.
- You need need need an accurate thermometer. I used an infra red digital gun thermometer, they're cheap enough now that I would recommend anyone gets one, they have so many uses.
- You also need a stopwatch or timer.
All ready? Take them to the bathroom. And now's the time to be thorough. Remember, if just a couple of mites survive, you're going to have to do this all over again. And trust me, you won't want to do it all over again.
Run the bath to as deep as you can and you need the water to be 43 degrees C. Not 44, not 42. You need exactly 43. Now, don't worry about maintaining that temperature once the plants are in, you have a bath full of water, it will stay hot for a while, trust me. But bear in mind the surface will be cooler than the bulk of the water, so swirl it with a stick. Use your hands if you like but I found 43C to be quite uncomfortable.
Once you're at 43C - put your plants in and set the timer/stopwatch. You need 15 minutes. No more or less.
Now is also a good time to wipe your windowsill, window surfaces and/or spray them with dettol or other bleach solutions. I really don't know whether broad mites hang out away from plants, but it's prudent to take a few minutes to clean up, it can't hurt.
When 15 minutes is up remove the plants, stand them up, and don't be surprised if they look like boiled cabbage.
Now be warned. Your chilli plants won't much like 43C either. All my plants lost their leaves. All of the leaves dropped off within 24 hours of the "dunking". I thought that was it, I'd killed them. But alas, they all survived, new growth came in very soon, within a week, and that new growth almost invariably came with flowers!
..also I have a youtube vid of the broad mites under a usb microscope if that's allowed?
p.s. that looks pretty advanced in your pics, I'd defo get out a "loupe" and go over all your other plants with a fine toothcomb to be sure you dont have others in early stages of infestation...they are sly...very sly...
p.p.s. please go easy on me, I'm a chilli growing noob, unfortunately I just had a gutting first year of being thrown in the deep end last year!
but the broad mites vid is quite interesting, I could only get a vid of a "drowsy" one, usually they move like lightning across the leaves. I believe this is an older infant. 
. I have mites on my sunrise scorp. Plant is NOT gonna like treatment, and I'm gonna miss a harvest because of it.