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...........
Check for damage at the base of the plant. A wound could have allowed a fungus infection to get into the wood. I would recommend you remove all the branches that have discolored leaves. Good luck, and let us know if the plant recovers! Skimmia is such a lovely shrub, I wish I could grow it in this Zone.
My reference book tells me Skimmia comes from Japan, where it grows on slightly acid soil, in woodlands. It should be hardy in your Zone, and would do best in dappled shade. Summer heat and drought might be an issue, but if you can grow Japanese azaleas and rhododendrons in your area, Skimmia should do OK.
A couple other plants died there after it, but now some Packera aurea is very happy there.
