I have had a lot of Java ferns closely planted on some driftwood, and now, a couple are starting to turn brown at the base, and rot away. I thought it was just old plants dying off, but now, new leaves are browning too, leaves that are still translucent at the tip and growing. What's the problem? It looks like the ferns are losing their clorophyll, and no pearling is coming from the brown. The green part of the leaves is still pearling though. Should I cut and remove the brown leaves? It seems like it's a spreading disease, moving on to other leaves every day.