Does anyone know why my leafs are yellowing? Manly at the top of the plant but In the middle on 1 plant, they're 3-4 weeks in flower,theyve also got some burn tips.. I'm growing on coco, EC 1-1.1 PH 5.8-6.2 was using 1/3 strength general hydroponics so lowered it to 1/4 at, the odd plant is...