Holly tree leaf discoloration
Holly trees normally drop some old leaves this time of year. The leaves first turn yellow and often become spotted with various fungal spots as they weaken, preparing to drop. It is all normal. This explains further: http://extension.umd.edu/hgic/topics/normal-leaf-shedding
Even though hollies are evergreen, they still drop old leaves. If they put out a lot of leaves in a particular year, then a few years later when that year's leaves are old, the tree will seem to be dropping more leaves than usual.