Hello Jerry, Thank you!
they have been growing in incubators in grow tents, 27c daytime for 16 hours a day, 20c in the night. They get LED grow lights, with shade cloth first few months. No heat mats needed in the tents. I did use Chinosol (fungicide) the first 2 months, but stopped after i got this dammage in the start on my copiapoa (i thought it was dammage due to, to low PH becouse Chinosol is acidic) and roots on affected plants was werry small and short. But now seedlings only 14 days old still get this dammage and i have not used chinosol on those. I use Demineralized water at 6 ph. I fertilise once every 8 days with a 1/10 cacti fertilizer. I also use Horsetail extract at half dose, after i stopped with the chinosol, for an organic substitude. when fertilizing i add a bit of tap water to get PH up to 6 ph again, (ferts drags it down) Also i water in the trays, not from the top. On my Copiapoa and Euphorbia all sub species are hit with this sickness. But on my Astrophytum and Ariocarpus there are nothing to see, and they have been sharing boxes. But i know that spider mites can be picky, but the lack of any visible mites in microskope makes me think it could be one of the tiny mite species, but i cant find much info on those.
Also been thinking if it could be some fungi, but it really look like mite dammage to me. English are my third language so please ask if something dosent make sence ^^
