Holly leaves tend to last perhaps 2-3 years before the age out and drop in the spring. They do often get spots, or get winterburn damage prior to dropping. This isn't a huge concern, but if you want the holly leaves to decompose faster (takes 2-3 years or longer) you can mow/shred them up. 

You may have sooty mold which is caused by scale insects, aphids or whiteflies feeding and excreting a sugary mix which can grow this mold, If they are on the holly, it could be dripping down onto the leaves below, enabling sooty mold to grow on them.

In cases where you suspect a fungal disease is afflicting a plant, you do want to sanitize the area around the plant by raking up and disposing of the leaves that have fallen  or picking off the spotty leaves that have lodged in branches as they fall since those are a source of reinfection year to year.

Growing new leaves requires much moisture which we are lacking with the Maryland ongoing drought so do not slack on keeping these plants watered. 

Sue