I have a few suggestions for you.
First, the light: Life Glo are excellent plant light tubes (the best in my humble opinion) but you may not have enough intensity. The tank is 50g, but can you indicate the dimensions (length, width and height)? I may have a suggestion afterwards. Also, are these regular fluorescent tubes, or T-5 tubes?
Second, you don't need CO2, it would not help at all with the low (relatively) amount of light. Plants require light, CO2 and macro- and micro-nutrients in order to photosynthesize which is how they grow, by converting sugards into energy through photosynthesis; these things must be in balance, meaning enough of each to work together. In low-light tanks, the fish and biological processes provide adequate CO2; adding more would be a waste since the light (and other nutrients probably) would not balance it. Other nutrients might be needed in the form of liquid fertilizer, and Seachem's Flourish Comprehensive Plant Supplement is in my view the best. It has all the required nutrients and in the proper balance that aquatic plants need; 1/2 tsp each week, or possibly twice a week, would be sufficient in a 50g aquarium.
Third, the plants you mention will (should) grow well in a low-tech system, provided the light is adequate and possibly with liquid fertilizer once a week. That's all I provide in my tanks, you can see the photos under "My Aquariums."
Fourth, and this is something that could be a factor along with the light, is the high pH. Except for a very few plants, most aquatic plants come from waters that are slightly acidic (pH below 7.0) and soft. However, most will adapt quite well to slightly basic (alkaline) water in the 7.0 to 7.8 range. Having said that though, 8.1 will probably still work once the light issue is resolved, and we can look at plants that fare better with a higher pH. As for altering the pH, it is generally better to go with what comes out of the tap, fish and plant wise, rather than trying to alter it. So, before we look at that, do you know the pH of your tap water? And what fish are you keeing in the tank?
When we have the tank dimensions, type of tubes, pH value of your tap water, and the fish you have, more will follow.
Byron.