Mulch holds in moisture, which is good in hot dry climates, but not if you've had a lot of rain. Impatients can't take an overload of water. They damp off and die. Clear the mulch from around what's left of your plants and let the soil dry.

I'll give it a try, even though the soil was/is not overly moist. Thanks for the response.

Besides my EEs and Cannas, Impatiens are the most water demanding plants I have. It's not good for any seedlings to be overwatered but I don't think you can overwater mature impatiens unless you have them in a drain-less container.

Taz--
I don't know where your impatiens are but my north facing, total shade impatiens require very little water. For 1 thing they are in the shade so they don't dry out as fast.

Last year we got way too much rain shortly after they were planted and I lost a bunch of them from damping off. These were mature plants all ready flowering plants. One day they looked fine and the next they were laying on the ground dieing. So yes you can overwater Impatiens

Damping off and root rot are not the same. My soil drains too fast to get root rot. I didn't know mature plants could get damping off.