hmm im not positive but it kinda looks like nute burn? but it looks like its only on one side of the plant? you're plant looks like its really starting to flower so maybe you gave it too much nitrogen...not sure tho.
pull of the dead leaves and if it continues to spread, try flushing it. it'll take a few weeks but once it recovers it will be fine. you'll think its not doing anything and then one day it will start growing again.
second opinions anyone?