What are these white dots?

lockout or deficiency... consider recent behaviour. Guessing a bit because color of lights could be impacting color. looks like Ca, but more often than not this is due to locout than a deficiency, despite what the marketers of Cal-Mag will have you believe. check what you feed. if Ca ppm is 100-120 i seriously doubt it is a deficiency... i'd wager a p/k booster is invovled? those will lockout other things very easily. more is not better... optimal is best... and sometimes optimal is a bit less. p - 50-60 ppm (when providing all nutes, ie hydro/soilless.. also when yo believe your soil is no longer providing nutes) k - 180-200 ppm. if way off from that and not related to substrate needs, that's probably the cause.. eliminate possibilities before making a decision. there are numerous factors that could impact this... no matter waht i say, do the due-dilligence... look into what you feed last month or two.. consider any other behaviours in that time... check pH make sure it is proper for yoursubstrate ... that alone can cause any and all problems. if you are the type that always adds things.. which is fine... just consider that tenency and lean toward lockout when you see issues. if you provide a balanced feed it won't be a deficiency.. it'll be pH or balance of concentrations of nutes.