Identifing Nutrients deficiency?

Minor damage like this is nothing to worry about, it can be caused by the most harmless things and will not affect over all plant growth or potency. Something like this can be caused by over lapping leaves and it does look very much like a moisture induced die back. Yes, I too would very much urge you to not defoliate, your plant needs every leaf she has to make the energy she needs to grow her biggest and best flowers. If she didn't need the leaves, she would not have grown them in the first place! Hope this helps,........... Organoman. (and staunch anti-defoliation advocate!)

Don't worry about that. Very minor, unlikely to be a concerning nutrient issue, more likely heat/light related (like a reflective hotspot, or it brushing against something, etc). Also, judging by the look of that plant, PLEASE don't defoliate it.

I totally agree with the other comment it does look light water or feed may have got onto that leaf and stained it Good luck with your grow 🙏

Dont look like a defiency to me rather something has stained that leaf maybe a drop of your feed ended up on a leaf ? if its the only part on the plant I would suggest its nothing sinister most probably just an old fan leaf. Your plants looks really healthy so I wouldnt be too concerned now you have taken the effected part off and if it has not spread its probably just an environmental factor my top guess anyway that leaf looks perfectly healthy no light or dark greens so yeah thats my best punt at this one my friend :)