Plant deficiency?

Apologies if this is in the wrong thread/section.
By no means am I an expert in growing cannabis but have grown quite a few plants and never really had this issue. This liberty haze is pretty fickle compared to other plants I've grown. Seems to be suffering a deficiency of some kind. Would be awesome if a bit of knowledge and advice could be shared to a fellow grower. Thanks in advance.
Thought I would add that I'm not sure if it's nitrogen deficiency since the soil is pretty rich but I have started using seaweed solution as food and that's all shes had in regards to food.
Cheers.

I just realised there is a plant problem forum so please excuse my error and if a mod could possibly move post to that section (if possible) thankyou.

magnesium deficiency.