Hi Katherine, You may have hit the reason. One of the most common reasons for roses not blooming well is the use of high nitrogen fertilizers or the over use of them. This will result in few to no blooms or small blooms and lots of foliage. Use a well balanced food or fertilizer when feeding your roses so that all of the rose’s nutritional needs are met.
Black Spot: Rose plant leaves with black spots that eventually turn yellow have black spot. This is often caused by water splashing on leaves, especially in rainy weather. Leaves may require a protective fungicide coating, which would start in the summer before leaf spots started until first frost. Thoroughly clean up debris in the fall, and prune out all diseased canes.