Answer: Sedums generally grow best in an open location in full sun, so it is possible yours are in too much shade. When grown in shade the foliage tends to be softer and more susceptible to insect attack such as by aphids as well as to fungal infection. This is particularly true if they are over fertilized and/or over watered. If transplanting to a sunnier location is not an option, you might try thinning them and doing whatever possible to maximize the air circulation around them. They should also be divided every few years to help them stay vigorous.
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