leave problems...mg?

just started flowering this batch in ebb and grow with rockwool. Day 4. This problem started a few days ago and has gotten worse by the day. Only see this problem in 2 of the 7 plants, but they are my weaker strains (vanilla kush)

feeding house and garden aqua flakes a/b and calimagic during the transition from veg to flower. I am thinking mg since calimagic is high on calcium. I did do 48 hrs of darkness before starting flowering.

also, just checked some runoffs a few days ago and they were above 6ph. Still figuring out rockwool, just switched to it for this grow. I top fed/flushed until they were 5.5ph. vanilla kush might just be sensitive.

i dont understand the 48 hours of darkness. its a waste of time and adds additional stress to the plants. imagine your metabolism stops all of a sudden for 2 days. looks like a problem that can be fixed with cal mag or epsom salt

Looks like a ph issue. Try to be more accurate and have it at 5.8 right thru.