Nitrogen toxicity ???

Downward leaf curl AKA the Claw indicates there is a problem within the root zone, usually it's from overwatering or soil toxicity. If your growing in soil do not give nutes with every watering you only do that with Coco, and are you checking your ph & ppm, also when you water do you give enough until you get aprox 20% runoff this will prevent a lot of issues from happening especially with build up, the best way to tell when to water is by weight try to get a feel of the pot when dry compared to wet. And if your growing in Coco then you need to add some CaMg because Coco holds onto it and only releases it at maximum holding capacity, only give half the amount of nutes required never the full amount unless you know that strain can handle it. Key points - give only half the amount of nutes required. - don't give nutes everytime you water with soil check runoff ppm first. - for coco give nutes with every watering plus add some CaMg. - water less frequent but give enough until you get runoff, aprox 20%. - keep ph between 6.0 - 6.5 & ppm around 400 - 600