This happens with almost all my Drosera except my pygmies.
I put any Drosera in a tray of distilled water... This has been done with multiple container colors, sizes, ect. I fill it up to almost the top of the container and I either keep it at that level, usually over an inch below the pot rim (used to do that, but stopped) OR I fill it to that level and let it drain dry before watering again. Result: Drosera leaves turn black from tips to base.
I put any Drosera in any of my Sphagnum cultures. I keep the water level about half way between the bottom of the container and the medium level. That is about 1" or 1.5" of water, sometimes more and sometimes less. Their roots are likely submerged or partially submerged in water, with frequent culture floodings. All Drosera in these conditions thrive. Temperate or tropical, they thrive. Some grow naturally, springing up from seeds that were in the Sphagnum. I have found sarracenia and VFTs in there, but mainly Drosera. There are spatulata, capensis, binata, rotundifolia and many other unidentified species growing. No matter what, they thrive.
72-82F during the day and 54F at night year round, with minor temperature variations due to season. 60% humidity and higher during the day, 70% in the evenings and 90% at night on average. They are growing in a greenhouse with my highland Nepenthes, which grow great for me. 50% shade cloth Arpil-October, lower light levels in the other months.
As you can see, there is conflicting information in me experiences with how much water they can handle. Was wondering if anyone could provide advice as to how to fix this... I'm sure it has to be water. It wouldn't make sense that all potted Drosera do this and ones in Sphagnum cultures don't, it has to be water... Any care tips for Drosera (I guess it is kinda late for that now that I own a ton of them lol) would be great. I know I'm really... derpy... for killing Drosera. Especially capensis, I have killed those too (but brought them back)... When my Drosera lose all their leaves, I move them into the Sphagnum cultures and they come back magically.
TL;DR: My Drosera turn black from the tips to the base of the leaves. What could cause this?