Because anubias as so slow growing they seem to be a target for algae. I find I usually get diatoms on mine, even in tanks with only natural or ambient lighting.
Try cutting down on your photo period (do you know the K rating and wattage of your lights?) but if that doesn't do anything, you may just have to just gently wipe the diatoms off during your regular tank maintenance.
Diatoms are fairly common in new set-ups and may also be caused by excess silicates. I always have diatoms of some form in most of my set-ups. It is unsightly, but easily removed with my hand or a piece of filter sponge.