Yello -
So I just went though this madness - i've been in 12/12 now for 4 weeks, and they attacked two weeks before 12/12 - and I still spray for them. Though the last one I found alive was two weeks ago.
For a closet grow - and depending on where you live (temperature and humidity) - you may always be battling these bastards. It's a fact of life for growing...as a newb myself, this is what has been repeated to me on repetition...you manage the issue, not treat for it. I live somewhere where it never freezes, so these guys are even outside, in your rugs, etc. especially if you have pets (and I'm in a pet friendly apartment!) They even can come in through your air intake in a tent (like mine)...so I've now put a carbon filter from my compost thing, put two unscented dryer sheets on both sides, and then capped my air-intake, so at least my intake is secure.
That said - I don't recommend using lady bugs on mites...aphids and thrips, sure. But mites reproduce too veraciously for a lady bug to keep up with it. So you'll be throwing money at buying live bugs when you could
proactively declare war on the mites.
*Mites reproduce in 3 day cycles, hatching, immediately laying eggs, then dying in three days, the eggs then incubate for three days then hatch....so it is important to kill the parents, then once the kids hatch, off them as well. Then, if any of those borgs laid any eggs, you get their kids once THEY hatch. This repeats until you don't have a mite problem.
SO I bought this stuff from my local hydro store...
http://www.mightybomb.com/ And there are many different versions of "this" - primary thing to look for is Peppermint, Lemmongrass, Rosemary, Geranium, Neem, etc. oils in usually 0.5-0.2% concentrations - and they all have different fun names. Just look for the $$ and then look at the ingredients. Totally organic and you can use them throughout flowering, if you use it right.
For like 50 bucks, I got a two-gallon container of it...it's not diluted, so you can dial in the strength needed. You spray two days in a row
right before lights out (make sure your fans are off) and spray the undersides of every leaf, then the tops to make sure they are completely drenched. I throw a towel in the bottom of my box because it'll get wet in there.
Let 'em air dry for a few hours, then plug the fan back in to drop the humidity again...because it'll spike.
Key Points to spraying anything on plants - do it right before lights out and do it without your fan off. This will allow for natural evaporation to occur without stressing your plants too much.
Do that - 2days on 2 days off, and repeat - and you won't have a mite issue anymore.
ALL OF THAT IS TO SAY - WHEN YOU BUY A CLONE FROM ANYWHERE OTHER THAN YOUR OWN GARDEN YOU WASH THE SHIT OUT OF IT. I will, from now on, spray every single plant that comes into my grow box with an oil concentrate/h20 mix. Some people even make their own out of habanero peppers, cayenne pepper, and peppermint oil. Scorched Earth.
I hope this helped. Next time, get a pocket microscope, scope the undersides of your leafs, especially along the main leaf vein, EVERY DAY until you stop seeing them. Keep track of how long you've sprayed for, and try to get it under control by the time you're ready to flush your plants - just in case some are left, they won't take over your buds in that last week. Once you harvest, they will leave.
Peace and love and good luck,
Smacks.