Hey looks like our anubias are in sync. Nice one. Your photo shows the flower way better than mine. Photography will never be my strong point.
If the brown on the leaves wipes off easy then it is probably brown algae diatoms. An oto would take care of it in no time. If it doesn't wipe off then it could be some kind of deficiency.
Congratulations to you both. I am pretty new around here but I am very impressed. Otos are a plant lovers dream. Anubias's best friend. Care takers of the Egyptian god of the underworld.
Is there any particular season that anubias' flower?
And the brown stuff is algae. It grows on the leaves because anubias is a slow grower, and not able to keep up with the algae. Getting a few algae eaters like otos might help. Also, try to keep it under the shade of some taller plants.
btw, how tall is your anubias? Mine doesn't grow tall, even though I have 2.8 WPG...
My brother's cichlid tank anubias has this problem too, but he has no small fish to eat the stuff. You can rub a bit of it off, but it's hard to do without damaging the plant