I had two very different drosera die rapidly, actually overnight.
My Manni and Venusta both died. They were both growing very slowly for months. Today I checked on my plants and they are brown and show no signs of life. The venusta bothers me the most because it was from seed. I had two come up. The first died and disappeared with in a few weeks. At least I think it died because there was no sign of it.
These two plants were kept with my other drosera which are doing very well and are flowering. They are all being watered by the tray method.