Rose Gardening Community

It's not blackspot, rust or mildew...I know what they look like.  This is brown patches around the edges and some on the main part of the leaf. The plan it bearly 18 months old, is planted in good soil & a sunny location. Could it be getting sunburnt? I only use organic products (no harsh or toxic chemicals) but it looks like burns or frostbite. It's on about 50% of the leaves and I'm rather worried. Any ideas?????

I have heard of watering rose bushes in to hot afternoon sun, the water magnifying the suns rays could burn the leaves. Where do you live? Is it that hot where you are now? Try watering in the cool of the evening. Hope this helps.