Durban posion, extreme deficiency?

Been growing Durban poison for numerous cycles and have never had this problem. We feed them age old when in veg, and tiger bloom and cal mag when I'm flower. Not sure what the problem is but whatever it is, it had an extremely quick onset. Any ideas what the issue is? Haven't tested the ph but we've never had a problem with nutrient uptake before. We also have been foliar feeding with cal mag since the first signs of the defiency.

Looks like a pretty serious light burn but most likely nute burn maybe both what lights how much nutrs per feeding?

That would be strange if it was light burn, as the canopy is about 3 feet from my 1000 watt bulbs. but we use under the recommended dosage for all our nutes to avoid nutetrient burn. I'll try flushing and see what happens. Thanks for the reply