DO you see the spots on leaves exposed by lights ?
Do you use RO/destilated water?
Flush your system with clean, pH'd water that contains a regular dose of nutrients that includes calcium.
This will remove any nutrient salts that may be affected the uptake of calcium and help restore pH to the proper levels..
Just remember :
Calcium, magnesium, and iron deficiencies often appear together in cannabis.
So look for Cal & Mag nutrients