Have any of you ever had sedums to actually die? This is mindboggling to me, as I have grown various sedums for years and couldn't kill them if I TRIED! But, all of the sedums around my mailbox are literally rotting from the middle outward. Weirdest thing I have ever seen. They get full sun, it drains well in that area (I didn't amend with sand there, but didn't feel I needed to, as, again...other plants that need well-drained soil have done well there.), and they were mulched with pebble. Here's the only thing I can think of: dog pee?

We do have a couple of neighbor dogs that run around (their owners are nice people, but I really get irritated about their dogs...supposedly there's a leash law, but you'd never know it) and I guess they could've "eliminated" my sedums. Hahaha... But, the other plants (candytuft, lemon thyme, mexican feather grass) seem to be doing OK. Maybe the sedums are just lower and more susceptible to the...er..."flow?" Or, am I completely off-base and something else is wrong?