Did you see any signs of yellow spotting before you observed the black spots? Just wondering.

What size were these plants when you purchased them? Has an excess of foliage dropped over the past few months?

There are several foliage diseases of holly, including one called 'tar spot', which is quite common in some locations. That's the first thing that came to my mind.

I'd take some samples to the local extension office for proper identification. Perhaps the extension agent could send them off for analysis.

Improper planting procedures can cause plants a great deal of problems, making them more susceptible to disease infestation. Planting too deeply, for example, is a real no-no. (Not saying that you did this!) So is using anything but the native soil in the planting hole, believe it or not. It's been shown that permanent plantings do much better at becoming established if installed right into the surrounding soil, with no added compost (or anything) for 'improvement'.

It's a different story if you are preparing an entire planting bed, but the hole-by-hole method is pretty basic. Dig the hole as WIDE as you want, but only as deep as it needs to be for the soil ball to be able to be at grade level or a bit higher.

Your disease may have come from the nursery, by the way. I wouldn't assume that you've installed them into a 'sick' location. Getting a good identification will help find answers.

No yellowing noted, no foliage drop off. THey were gallon size plants. I don't think they were planted deeply. My son planted them and he works for a nursery planting trees and shrubs. We did mix in a little compost because the soil was very hard and clay but he is a believer of using as much of the native soil also. They came from Lowe's, not a name brand nursery.

I field grow different varieties of hollies. My Nelly R. Stevens leaves are covered with black spots. I to was concerned and began calling other nurseries for info. Several told me this was common and nothing to worry about. I hope their right.

Here is a link that might be useful: http://peterstreefarm.com