|For the past two years my ivory rose bushes have had a purple/burgundy "stain" on the edges of buds and blossoms. Some buds do not open and those that bloom have dark edges or darkened centers. The bushes appear to be hardy and no problems with black spots.
|This sounds like the work of those nefarious flower thrips, tiny juice-sucking insects that infest the buds. And they are especially fond of light-colored flowers. You can control them by applying insecticidal soap sprays frequently to the unopened buds. A neem-based repellent may also work to keep the thrips at bay. Good luck!