My vote would be related to PH issues, do you happen to know what yours is?
Try a marijuana related search on google involving white spots + ph, it may give you some insight.
Cheers,
Re: Help please... Yellowing and claw like leaves?
I've had similar to something like this in the past, from what I remember it may be a Potassium deficiency. Yours seem to be curling down rather than up, but I find that is more dependent on how the leaves start to dry.
Cheers,
From looking at the first picture, it seems your blotches have a purple tinge to them; if this is the case my vote goes to Phosphorus deficiency. Growth would also be slowed drastically, with red stems on the fan leaves as also shown in your photo.
"Leaves turn bronzish-purple, contort and...