[jdm68]

So I have read some past posts about anubias getting brown spots on the leaves, and it seems to be the consensus that too much light is generally the cause of it. I've got mine in a 2 gal bowl with a 13w 5500k CFL over it. Could that be what is causing my problem as well? I do have a pretty good layer of duckweed growing on the surface to diffuse the light...

 

[jdm68]

Here's another shot...

 

[flip9]

With excess light, i always get green spot on my anubias.

On the photo it looks a bit like diatoms to me. Have you tried rubbing it off?

 

[gordonrichards]

looks like diatoms to me as well.