i have Cyperus alternifolius (Umbrella Palm) in a vase in my lving room. I put plants surrounding my turtle tank for a more natural look.

anyway, i had three of this plants in one container. the roots and pots were covered with water. i left it for about 3 weeks and i noticed that one of the plants had dried up.

i removed them from the water to let them dry out a bit. i noticed that the dead one, now had fungus all over it. that must be what caused it to dry up

my questions are, is it dead? and should i spray the others with something? what kills fungus but leaves the plant in tact?