Yellow Marks On Leafs One Plant Only

[Jezza99]

Can someone tell me what this is thanks they are a out 20 days old.

 

[DrMcSkunkins]

Sprinkle a handful of garden gypsum on top of the coco or dirt? before next watering and foliar spray with a litre of water and two teaspoons of epsom salts mixed in right before lights out, that should help.

 

[DrMcSkunkins]

Are you using calmag suppliment and what are you feeding?

 

[Jezza99]

Are you using calmag suppliment and what are you feeding?

No calmag supp just plant food 24/6/12 every week

 

[DrMcSkunkins]

No calmag supp just plant food 24/6/12 every week

Liquid all purpose plant food or crystals?
You need a 2 or three part fertilizer for cannabis, and calmag, especially if you are using a soil less mix like coco.