4 Strains, 2x4, LED grow

sooo it is day 38. since my water filter was saturated, and I fed some days with base EC of .8 , (meter defective and I had to wait for new water filter inserts) I thought it would be a good idea to use one watering Florakleen to dissolve the carbonates and then flush it with .5 nutrient dosage... result was a bad CA deficiency immediately. brown spots on leaves... and some yellowing. oh well... luckily those plants are bushes, so should be plenty of leaf surface left for finishing with a decent result.... I also removed some undergrowth, that was already dying from the plants sucking out P for the flowers... I am a chronic under- feeder. then I encountered spider mites... some slight webbing too. (see pic). only on one plant so far.. which is weird. as usual the predatory mites do not work that well.. I decided to not spray them down preventative with pyrethrum/oil, one week into flower (only slight pre flowers), instead I've ordered 2 times the predatory mite package. 50 bucks down the drain. i think the 1st box I've ordered, almost all mites were already dead due to hot weather shipping conditions... I applied californicus 2 times, and that other species that is known for fast killing of the mites once... did not work out that well so far.. more thrips also spotted.. same shit everytime.. I regret not spraying at the switch to flower. always the best idea, even without any visible infestation. next time I'll do a better job at this... prolly DWC too, 4 plants:) some random pictures for you guys... oh and I bought a power meter... had the lamp at 300W so now I now I dimmed the light just perfect.. now running at 320W. the last days were pretty chill, about 20 to 24 °C here, high humidity too. so that should help for the spider mites, I decided to get some isopropyl alcohol, and spray them at 10%ISO/h2o solution the next days. buds are still pretty small, and I guess that 10% alcohol in the solution should prevent the buds from gettingany fungus... I will spray in the morning during lights on, (dimmed down) and before the evening probably..not gonna let them be wet during night cycle.... still have to wait for that ISO though. so far still acceptable.