Sudden Black Leafs?

[razer121]

recently ive noticed one of my plants in my tank has started to go black...im unsure what is causing it? all my other plants seem fine? and when i say black i mean solid black! i took the plant out of the water to further look at it and it felt the same as usual (pretty stiff that is) im starting to wonder if this plant is not ment for a tank...anyway heres a pic of the plant itself...

of course that is an old pic of the plant, now most of them leafs are black does it look like its ment to be in water? thanks!

 

[aaronnorth]

it looks like an anubias sp.

the rhzome isnt meant to be buried. it should either

a) be tied to a rock or stone

b) plant the roots only, leaving the rhizome sitting on the substrate,

 

[razer121]

the bottom has been pulled out of the substrate ive already been told that one lol, erm well it seems ok i obviosly didnt notice but there is a new leaf growing in the middle, really odd...also noticed anouther one of my plants leaf has started to get the horrible black look aswell......is there a possible infection going on here???