I have two huge beds of impatiens in my yard. One bed, however, has developed some sort of malady that I've never experienced before.

The leaves are turning black, going "soupy" and the plant is like dying from the top down. I know impatiens get leggy this time of year but this is entirely different. And they are still blooming nicely (except for the diseased ones) so I don't think I need to pinch them back just yet.

They get plenty of water with the watering system since they are growing in full sun. Should I fertilize? Spray with a fungicide? I don't detect spider mites or white-flies.

Mimi