I wouldn’t say smashing it just yet. That problem I spotted the other day has now started effecting new growth. I completely forgot to snap a pic of it tonight but I will tomorrow. It’s really skinny, looks rippled and burnt. This has only happened since I sprinkled DE on the coco. I’ve looked high and low on the net and can’t find a single adverse reaction to DE documented. So maybe it’s coincidence. But anyway by images it’s either an iron or phosphorous def. I’ll give them a flush tomorrow and see what happens.
a flush is the best course of action. its likely just a PH issue, check your runoff PH, i have never used DE but if it is high in silica it could be altering your PH as it passes through the DE.
also check your PH pen calibration.
the other thing is if you had fungus gnats bad it may have been that you got to them too late and they have done some damage or the other possibility is fungus gnats tend not to be a massive issue in coco unless there is something bad going on in the root zone they thrive if there is any decaying rotting material in the coco.
i have always used baccilus to control gnats in the past works a treat. luckily i have not seen a single one this round. panthose over inlets etc seems to have kept them at bay. destroy any old root balls etc. when i first started out i was a messy prick and i would chop a plant but not get around to disposing of the rootball straight away as soon as those roots start to die off the gnats move in to eat the rotting roots. then they spread to your grow