Plants turning black?

[msouth468]

I don't know what type of plants I have (Got them for free from a friend). And I have had them for about 6 months now. And they are starting to turn black. What causes this?

I'm going to do a 50% water change so any help would be great.

It is a 29g tank with 6 mollies. Planted prettey lightly, only 4 plants all together.

Water quality is

ammonia 0
ph 7.0
nitrate 0
nitrite 5ppm

I don't know the KH or GH. I'm learning about it and I am waiting for my test kits to come in. But, seeing as I get my water from a RO filter, I'm sure that they are probably low. The only fertilizer I give the plants is Leaf Zone which has iorn and pottassium.

 

[IceH2O]

Does the friend still have some of the same plants in his tank? How are they doing.

My 1st thought is that they weren't true aquatic plants and are just dying.

My 2nd thought is that they're being covered with algae. Does the blackness rub off?

If its the 1st just take them out. If its the 2nd depending on the plant a bleach dip of 20:1 "should" get rid of it short term.

 

[msouth468]

No the black doesn't rub off. So they might be dying. I can't get ahold of my friend so I will probably just take them out.

Edit: I got ahold of my friend, he said that the plants were bulbs that came off of some sort of seed he got at Wal-Mart a year ago. The plant started to replicate and he gave me some. If that helps any.