Leocothoe can be temperamental plants. Firstly, even in the best of conditions they have a predisposition to leaf spot diseases. They commonly play host several fungal disorders, though only two of them are likely to be the causes of leaf spot symptoms.

Secondly, they can be pretty darned fussy about those conditions. Though full shade isn't necessary, they do require dappled or high shade in order to do their best. The soil must be very well drained, and slightly acidic. I think of azaleas and leucothoe thriving under the same conditions...no big surprise since they both belong in the same family.

Avoid overhead watering if at all possible and no crowding. These plants should be dry before nightfall. Both Cylindrocladium and Phyllosticta are airborne fungi. This means that they are highly contagious and easily spread from plant to plant. Remove any plant debris, as it may harbor spores, and keep your tools, gloves, and hands rinsed and even sanitized when moving from one plant to the next.

The act of cutting these plants back MAY have caused the plant to rebound with a dense flush of new growth. If this is the case with yours (that's what usually happens when we cut plants back severely), you may want to consider doing some thinning of your plants...just to insure that there is plenty of air circulation to the inside.

Fungal spores can remain dormant throughout the winter. You might want to consider spraying the plant before the new growth emerges in the spring. There is some evidence that occasional applications of neem oil can be effective in controlling these particular diseases. It (neem) certainly works for powdery mildew and black spot. Your copper fungicide is a good option, but never use it within two weeks of an oil.

Thanks for the response. I had no idea they were so difficult until after I planted them, but they look gorgeous when they're not covered in leaf spots. Luckily, they are planted in dappled shade on the north side of my house and are planted with several azaleas, who prefer acidic soil. I made sure to completely clean up the debris last spring when I pruned them. I heavily sprayed the plants and the soil with the copper fungicide and I saw no more signs of the leaf spots at all until now, so I feel pretty good that it worked. I have some neem oil, so I will use some in early spring.