Photos aren't very good. maybe varroa mite poop.
It dosent appear to be any type of brood, foul or otherwise. It's something stored in the comb.
"People will generally accept facts as truth only if the facts agree with what they already believe."- Andy Rooney
moldy pollen maybe?
Leer Family Honey Farm-Shannon Leer
That is very moldy pollen. Take your hive tool and scrape off the top and you'll see colored pollen below.
Not to worry.