It could be many things like a Nitrogen def, Calcium def, zink, Iron, or magnesium def. First I would try to get some dolomite lime to balance the PH to 7.0, then if that didnt work try taking like 10 rusty nails on top of you soil and leave them there for 1 week, if that doesn't work then try 1 tbsp of epsom salts to a gallon of water this should help the magnesium def. The last thing I would try is the Veg nutes that are high Nitrogen, but if it is a Nitrogen def the Veg nutes will help it alot. Hope I helped you out +rep appreciated.
But keep in mind that there are much more things besides deff that could be wrong like Pest, and diesease, or PH or root rot, or root bound, or bud rot, or light proximety to foliage.