yellow plant needs some help

this plant has just never looked great from the start, and its gettin worse. it was started mid october and is in mg time-release nute soil, in 5 gal grow bag. under a 600watt hps, temps average about 70 in the room. as far as nutes go I gave it a little tiger bloom (1\4 strength) the other day and looks a little worse.

any ideas ?? the plant is hangin in there but its very light green to yellow all over, and alot of the leaves have what look like burn spots.

nute burn from the soil ?

ph problems?

Ph is about 6.6 - 6.8 , its tap water that I run through a brita filter. As for nute burn it could be the MG soil doin its time release bullshit. Should I try flushing it with a couple gallons of store bought water, then transplant ?

im not an expert and im not sure if flushing will get the nutes out of the soil or just make more nutes get diluted.... im not sure how time release fertlizers work,