This has all the hallmarks of slugs, which you don’t normally see as an issue on sedum. This is because sedum likes to grow in sunny and dry conditions, and slugs need shaded, damp conditions. However, the irregular holes on the edges of the leaves are very characteristic of what slugs do. That’s stressing the plant, and the fact that it’s not in the ideal conditions, are combining to make it weak. I’m not 100% sure what the red stuff is, but it appears to be mold (also consistent with overly wet, shady conditions), or callous tissue from the damage caused by the slugs.