looks like nute-related.. probably a "bloom" formula instructing too much p/k or overall EC (concentration).
Dying sugar leaves can be a scary sign of bad things... so, find a spot yo don't care too much about and gently put the calyxes apart around one of teh dying sugar leaves... make sure there is no fuzzy white/grey growth underneath... if stem is clean 100% nute-related.
i'm 99% sure this is nute related... looks like burns, where as a leaf dying due to mold underneath progresses a bit differently
side note, you probably want to leave more fan leaves to power growth... that plant may take longer to finish because it's producing less ATP each day. ATP powers cellular growth. Less of it = less cellular growth. LEss leaf coverage = less photosynthesis (pieces atp together) It's good to keep good airflow, but don't decimate the canopy, either. looks like yo have 90% sugar leaves remaining or very small fan leaves that barely had time to grow before vege growth (stem elongation / leaf growth) ended in plant.