I've got a set up very similar to this tank, however the substrate is alot simpler. 1-1.5 inch Laterite

(dug from Werribee, an outer Melbourne suburb) With a good layer of mulm (fish only tank for about a year) and peat underneath. All capped off with 1inch 2-3mm inert gravel.
The tank has 2.5wpg t5 lighting and CO2 at 1bps (not sure of actualy ppm but will find out soon). This tank is mainly stocked with swords and they go nuts. This is the tank quite a while back about a month after set up
This is when it really started to grow
And now the swords are all trying to grow emersed. I will try get pics later.
The only water collumn ferts are NFS Cichlid formula, NLS TheraA and other treats. I feed very generously with an auto timer (5 times a day). I did put root tabs under each sword (Seachem Florish Tabs) but that was during tank set up and i havent bothered replacing them in about a year now.
Strange thing is i didnt get much of an algae bloom during tank set up (filters were fully cycled). I did get some green beard algae but that went away pretty quickly, then i went though a slow and long (2 month) BBA cycle. After that i only get spot algae when i am really lazy and let phosphates creep up to 3ppm. However your higher light might be diciding difference.