The set of leaves in the photo have subsequently died. Luckily not the entire plant though. Another finding in my research indicates that my plants may be experiencing nitrogen toxicity which would explain the brown tinges. My other plants have also developed curling at the leaf tips otherwise known as "the claw", apparently that is due to too much nitrogen. My most recent watering included quite a lot of nutes so it seems to make sense to me. Are you familiar with that problem?
I kinda got relaxed about adding a lot of nutes as the bottle said that its not really possible to over fertilize if you mix correctly. Perhaps I didn't mix correctly.
Here's a pic of the bottle with the nutrient content. Is this suitable for weed?
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I'll just cut back on the watering and the nutes.