thats PH spotting, your in lockout


complete a soil runoff PH test.......
with PH corrected water (6.5-6.8PH ) pour enough water in the pots so the water runs out the bottom of the pot ...collect & test the PH of this runoff water....

If the PH reading is out of optimum range 6.5-6.8 PH, you need to flush your plant.
Flush with PH corrected water, till in optimum PH range, 3 times the volume of the pots rule of thumb but may require much more flushing if the rootball is thick & sour

EG: 1 gal pot = 3 gal. flush

add 1/2 strength nutes to the last gallon of the flush.