Hi, Pat.
Dicentra don't seem to be very disease-prone, so I'd think yours is probably just taking a dormancy break. They're geared to sleep through the hottest part of summer, and since yours is in a container its soil is probably even warmer than one would be planted in the ground and mulched. You might want to reduce watering during this time since the plant isn't actively growing. Rot is the other possibility, though it appears
your potted plant(s) were healthy earlier in the season.
My in-ground plants have been dormant for quite some time now.
They don't get any supplemental water, so when conditions aren't to their liking they disappear until favorable conditions return.