Black spots on plants

[timwag2001]

I have some black spots growing on some of my plants. It almost looks like green spot algae, just black. It grows mainly on the leaves that are on the bottom of the plants.

Any ideas on what it is?

 

[mgamer20o0]

what plants?

 

[timwag2001]

Anubias nana, hygrophila compacta, alternanthera reineckii, and kleiner bar sword.

 

[timwag2001]

I was thinking something like black spot algae but I've had some trouble getting a hold of some K (just ordered some from rex).
Could it be a deficiency of some sort?

 

[Ivy]

I am curious about this thread, because my sword has developed black spot issues. All the other plants seem okay, but the sword is covered with them and the edges of the leaves are turning black. I googled black spot algae and the pics I found on the Anubias were exactly my problem. Not sure what to do from here. Ordered a whole rack of ferts from Dr. Foster and smith along with florish excel to add co2, but since I don't know what is causing this I don't know what to dose it with. I tried to get some pics, but underwater photography is not my forte (unless I am in the water). My plants look all green and beautiful in my pictures (figures ).