The "stippled" appearance of some of the leaves may indicate insect damage. I'm particularly sensitive to this because I treated for foliar disease for two years before discovering I had a spider mite problem. Some insects, like spider mites, are practicaly invisible.
Hold a piece of white paper under a branch above the damaged ones and shake it sharply. If you see tiny black or red spots smaller than pepper on the paper you may have mites. It takes at least a 15X magnifying glass to see the details.
Search the forum for Mites and/or insect damage.
Good luck.