Time for some updates:
After 4 weeks, growths in this tank is slower than I expected. The foreground is still not fully covered by the HC. Compared to my previous layout, the HC successfully covered my foreground in just 3weeks. At first I thought the problem is my lighting because the bulb I'm using is already more than 1year old so I added extra 20W 6500K screw bulb.
But still the HC did not show any improved growth rate. Then I observed that many new shoots emerged from the soil but not many visible new runners growing on top of the soil.
After I looked carefully, I realized that the shrimps actually moved the soil pellets around and the HC become buried beneath the soil that is why less visible HC growth. I sucked up the soil covering the HC every day and now more growth is observed. So hopefully in 2 weeks the foreground is fully covered by HC.
I'm planning to switch the stargrass at the back using plants with smaller leaves. Maybe
Rotala rotundifolia or
Didiplis diandra. I don't really like the stargrass because the leaves size is to big for this small iwagumi. Ludwigia arcuata looks good currently but man, this plant is also a slow grower. haha (I want everything fast!

).
Other updates:
-added 5 juvenile guppies from my other tank. 1 already died. jumper.

-no longer using the lily pipes because of difficulties during maintenance. Much easier to use current set up.
-the odd colored stone has been removed. Thank you for your advices.

but I can't find suitable stones to replace it..hmm..
-Started dosing 1ml Seachem Potassium, 0.5ml Seachem Iron, 0.5ml Seachem Fluorish for every 2days and 1ml Excel daily.
-CO2 set up at 2bps.
-Lighting period for 8hours.
Other photos:
Thank you for looking!

Comments and suggestions are welcomed!
Regards.