Hello,
Ok 3 tubes, do they have reflectors? do you know the wattage on them?
It seems like it is a low light tank, so plants that dont require so much light could grow.
The blue light is the least helpful for plant photosyntheses, it tends to encourage algae more.
You should really keep them all on for a min 8 hours a day although more often in planted tanks peeps keep them on 10-12hrs. I have one of my tanks with diy co2 on 8 hrs and seems ok.
If you can get the lights on a timer (from a hardware store) it would be better.
If you havent got any fert in the gravel it might be an idea to get fertilizer tabs or pellets and bury them in the gravel around where the plants are.
Not sure if you have vallis in there, but that usually grows quite well, Java fern and anubias tied to wood or rock will be ok in there. Various cryptocorynes will also be good particularly Wendtii and Becketti species which are fairly common.
You could make a simple diy co2 unit. Use a rinced Coke bottle with a pierced cap which you pass tubing through (cap needs to be sealed air tight) , other end of tube placed in aquarium, good to put a bubble diffuser on the end (easy to get in lfs). The reactive agent is 2 cups of white sugar dissolved in luke warm water and add 1/2 teaspoon of yeast.
When doing DIY co2 you dont want to over do it because you cant easily turn it off at night, but one bottle should be ok. You can also buy cheap co2 sets.
One thing at least you should do for plants is to give them a regular lighting period of at least 8 hoours with all the tubes on (pref change the blue one
).
If they dont get this then they will not be able to photosynthesis enough and harness energy to produce more cells etc to be able to grow.
Java fern would be great
just tie it with thread or fishing line to bod wood, it will evnetually root to it.