Thanks ADA, i'll try to give as much advice as i possibly can...
yes, plant biomass takes a while to start, but once when it does, it grows at an exponential rate and will fill out your tank in no time.
from what i can tell, many of the plants in this tank are very low maintenance in the following areas:
UG: no nutrient dosing, or negligent dosing (does not draw nutrients from the substrate)
but requires High lighting and High CO2.
Mini Pelia: versatile plant, undemanding in terms of lighting, nutrients and CO2.
Downoi: probably the most demanding plant in this setup: high Fe needed
Anubias Nana Petite: low light plant, but needs adequate Fe.
Rotala macrandra japan 'red': moderate lighting.
I hope you can see that the plants here are balanced pretty well. Anubias nana, and pelia obtain nutrients from the water column. UG takes nutrients from microscopic organisms, and Downoi and Rotala take from the substrate and water column. None of the plants are forced to out compete each other for nutrients. I believe this is one the possible reasons why they are able to do so well.
I have high lighting...im using a 36 W (10,000K/6700K) which roughly translates to 14.4 wpg---very high light indeed. i will admit that the mini pelia and the anubias dont like high lighting as much as the other plants.
My CO2 system is DIY yeast reactor, and i use a drop checker to check CO2 saturation levels...beyond that, i cant tell you much.
Water changes must be done weekly to avoid nitrate buildup which algae exploits.
That's really all i can tell you, i hope it helps.