So far, so good! A few comments however...
The rocks kind of have that chalky, limestone-y look to them. Did you test them before you put them in?
Your 3 spot/Gold Gourami will probably only get
more aggressive toward the other tank inhabitants, not to metion that it could grow up to ~6" in length. I'd consider trading it in for another Honey Sunset or Dwarf Gourami.
You haven't mentioned any ferts yet -- are you dosing them?
I've got nothing but good things to say about the Coralife T5 fixtures. I think they're a great choice for a 20L, as they're one of the few (if not
only) 30" fixtures whose bulbs reach both ends of the tank. Your hanging shoplight was a great idea, but you're really wasting quite a bit of electricity for the meager amount of light it's providing your plants. If you can relocate your HOB -- or better yet, get a canister filter -- you'd have room for a second Coralife which would lead to lush, dense growth
Back to the filter, it 's probably a bit underpowered for a tank of this dimensions. Once plant growth starts to fill in a bit more, you may find that there are "dead spots" with regard to water, CO2 and nutrient flow. Dead spots = algae.
Finally, speaking form experience, lots of stem plants in a 12" high 20L can be a
real PITA
Try to find some mid-ground low growers, some of the smaller Crypt species (Lucens, Petchii, Parva) work out really nice without a whole lot of hassle. Hygro compacta is pretty nice too.
You're off to a good start, can't wait to see what this grows into!