Please look under the leaves with a magnifying glass......flick a few leaves onto a piece of white paper......if you see see anything moving....we're talking TINY here,......it could be spider mites.........also, to me, it looks like some sort of herbicide might have been accidentally sprayed over it......otherwise, my instinct would to be to yank it out and hope for the best...it looks like it could rebound.......also check to see if local dogs are "watering it" on a regular basis...........
