Hi
@MrWeebles! This looks like a nutrients-burn to me. I see you're having burnt tips and edges on older/bigger leaves, those tiny leaves are just having a different reaction to the toxicity. In this scenario I would give it a good flush with only pH adjusted water (6.0~6.2) for at least a week, otherwise this might have a negative effect on the final product's quality. Keep us up-to-date and happy growing.
👊