it looks like a magnesium deficiency , trust me theres a lot to learn , im near finish in my first grow and i discovered wardrobes are not the best for growing . ill make a thread soon explaining my mistakes , i made a lot lol.

buy the growers bible by jorge cervantes , it is vital.

if i was you i would flush the pots incase theres salt build up, i read that you should flush every 4weeks , pity i was 2and a half months in when i read it !
the books says "treat deficiency by watering with two teaspoons of epson salts per gallon of water"