SullenOldGit

@Mr_Juice, Thanks for the comment - points noted!! In this particular case a bit of CalMag had it sorted in no time, plant looks really nice again. So no permanent damage done I think. I am thinking in future I'll probably add about 30% fresh substrate to the used stuff and as you say, some mycorhizzae etc. As for the humidity, I had a bit of mould on the last one - first time ever!! (I was so pissed about that!!) so I'm ok with the low RH for the moment. tbh, I haven't yet seen any adverse effect from the level of RH I have, which is pretty much the ambient level as I leave the tent open most of the day. Thanks and happy growing!! 😃 Edit; I just noticed the RH reading when the photo was taken, 37% is really quite low even for my grow room, its normally about 45% - 55%. 😕