The "dark green veins" is more likely (refered to as) "interveinal chlorosis", and the "brown spots/burns" probably fall into the category of "necrosis". Just in case those terms might help in your search.
I looked up interveinal chlorosis and seems its more of a yellowing either side of the veins. Mine is more normal leaf colour but slightly dark green veins. And not on all plants, just 1 or 2. I will see if they are still there are few days of additional cal/mag.
I am getting more convinced of not reusing the water but still want to know how long it can be done so if i go away i know the limit. Will contact the lab and find out what it will cost to measure all the nutes.
For those using drain to waste coco, what is your schedule, water Ec start point, what do you add in which order, Ec end point, how often you water, just at that point of drips coming out from the fabric pots or actual run off each time ?
So far here is mine for veg
2x day watering 10 hours apart give or take until 10-20% runoff
60 Ec starting water
Add Canna A + B until 1000 Ec, then Cal/Mag until 1200-1300 Ec
Days not using Cal/Mag i add more A+B until 1200-1300Ec.
Have no set protocol of what days i use additional Cal/Mag, usually if i see any deficiency. Maybe i should run it all the time, and if so at what Ec ?
Only new things i have stared to add is Silica, and I would like to add Humic acid.
I dont foliar spray yet but have a potassium (i think) glyconate wetting agent, which i will use with what ever deficiency appears.
I have read to only foliar spray after lights out but is this even an issue with LED lights that done cook the plants like HPS etc did ?