Judging from those sites I think your first guess was right... the .1% nitrogen of MGOCPM ain't enough for anubias? Maybe I should just move the plant to one of my tanks, plenty of nitrates in those...
I'm pretty sure most anubias roots cant be burried in the substrate. I think they're almost always supposed to be anchored to something like wood or rocks with the roots in the water column or else the rhizome rots just like java fern :/ I'll let someone else chime in to answer that one for sure.
I see a lot of wood chips and bark in your soil. It's a common misconception that these types of organic soils are nutrient rich. This is only the case after the organics have broken down and have been mineralized. You get an initial nutrient burst from the composted cow manure or pasturized chicken litter but after that initial period the potting mix is spent. The organic soils we use are useful under water because plants supply oxygen via the roots to the bacteria that break down the peat, bark, humus, and other organics in the potting mix.
Anyways, my suggestion to you is to use some liquid plant food and spray the anubias.
Thanks for the info. This is what I use in all my emersed setups, and all my stem plants grow like crazy. But swords and this anubias don't seem to do as well, must be their more nutrient-demanding nature... I'll look into liquid ferts, or maybe switch to my compost.
Definitely time for some root tabs man, especially if your swords are struggling as well. 3 of the DIY osmocote+ ones in my 20 breeder grow the swords an inch a week easy. My anubias coffefolia and nana are doing great too