Struggling with Peace — would appreciate advice

I want to be honest: I'm not getting great results with Peace and I'm not entirely sure why. black spot fungal disease on the leaves has been a recurring problem despite my attempts to address it. I've been focusing on deep watering at the base rather than overhead based on everything I've read.

dense double blooms with a classic silhouette is there in glimpses, which tells me the plant has potential in my conditions. I have it in a dedicated rose bed with good air circulation which might not be ideal. first flush of blooms in late spring showed some improvement. Two stars for now — not the plant's fault, but not a success yet. I'll update if things improve.