Couple of thoughts... excuse me if they are way off.
I think there are no real aquatic plants in this tank. So the whole discussion about light color, CO2, fertilizers and such is interesting, but doesn't really apply to this specific situation.
A clown loach in a 15gal tank does not work. Please return it to where you bought it from. Clown loaches grow easily over 10 inches, and really need a well filtered 100+ gallon tank, along with some like friends.
Silver Dollars need bigger tanks too, and will eat all your plants. Keeping "one of each" community fish makes them lonely and angry.
You could do some reading here at the website to learn about the basics. Somewhere you have to decide if you want live plants, then learn about their needs. Otherwise you will be wasting a lot of money.
There is no need to worry about the "spectrum" of your bulbs. There is no need to worry about CO2 in this aquarium. No need to increase plant mass at this time.
If you want a planted tank, first get rid of your over-sized fish. Then wash the whole tank incl substrate to get rid of most of the cyanobacteria. Buy a lot of aquatic plants (look for beginners package, hard to kill etc).
Before you do all of that, read up about substrates and fertilization. With lots of light plants will grow fast and need lots of fertilizer. Now "lots" can be very specific quantities, so don't ever think more is better.
Before you do that, decide if you want a high-tech tank (your light fixture points that way) which requires CO2 injection and NPK and micro dosing. Or sell the fixture and go with a less intense one for a lower tech tank.
Anyway, excuse the lecture.
You have come to the right place, but keep in mind to take all advice with a grain of salt or two. Listen to all opinions, but draw your own conclusions.