Some people do okay with liquid co2, but there is no real substitute for pressurized co2 gas diffused into the tank.
Here's a couple of things that I would recommend to think about
1. Pressurized co2 will make your plants thrive, much more than liquid co2 will. Its abit of an investment, but well worth your efforts. I had a lowtech tank for 3 years before upgrading to hightech and it makes a WORLD of difference haha.
2. Lookup Estimated index dosing method, it may look a little confusing at first, but there are several good articles on it. It is one of the easiest ways to get into adequately fertilizing your tank.
3. You can get dry fertilizers (much cheaper than liquid fertilizers) from members on the forum in the swap and shop( it seems like you've already gotten some of them)
4. Adding more plants will make your tank more stable as more beneficial bacteria (BB) will form on the plant mass, and also they will produce more oxygen in the tank, good for fish
I would reccomend adding the same plants your currently have, just like add another 2X of what you got originally. Specifically, I think that you have plenty of sword plants in there, but at this stage getting 3-4 more varieties of stems at 15-20 stems each would help the tank dramatically. Also I would add maybe twice as many grass tufts to your foreground. Here are a few suggestions (Ammania sp bonsai, Hygrophila corymbosa, Hygrophila sp. Brown, Ludwigia sp. red) These are all stem plants. If you look in the swap and shop on this forum, or put a WTB add in the WTB section, you will get much healthier plants for much cheaper. Members here have really good plants and usually really reasonable prices. Let me know if you need help in choosing.
5. You are going to notice that your sword plants will begin to grow straighter leaves and shed their round leaves. This will be normal as they are shedding their above water leaves (emersed leaves) and going towards their underwater (submersed leaves) leaves.
6. Many loach species eat snails, and also, kuhli loaches aren't really a clean up crew. The Best "cleanup crew" that I've found are Bushynose plecos. They are much prettier than normal plecos and my opinion and much cleaner. The reason someone suggested taking out the normal pleco if he is in fact a common pleco, is that they are POOP factories. They are pretty nasty buggers that will poop very similar to gold fish (another nasty fish) They may be cool to look at, but trust in the long run, getting 4-5 bushynose plecos will do way more work, and be much more beneficial to your tank in the long run. But its your tank with your fish, do what you will haha, just thought I should warn you.
7.Lighting should be fine with 2 bulbs, but cut your photoperiod down to about 8 hours instead of 11. Even with co2, 11 hours is a long photoperiod, you will most likely find that algae grows really fast at that rate.
Hope all is well,