I had to rearrange a little because I realized that my bunched plant, Anacharis, can be planted stem by stem. So I separated it among my three tanks. Just one tiny stem in the betta tank, just as an experiment.
Also, don't know if anyone has any info on DIY Co2 maintenance and recipes for 2 litres, but I'd be grateful if anyone chimes in on that since I'm working on getting that together as well.
Adding CO2 is probably not going to do much of anything to your tank.
Based on the 3 tanks you have, the OEM lighting that comes with those hoods don't really give off enough light for those plants to FLOURISH. Adding CO2 can create major algae problems if you don't have enough fast growing plants to absorb the excess nutrients.
If you haven't done so already, upgrade the bulbs to 6500k.
Java fern grows REALLY slow. Near impossible to kill unless you bury the rhizome.
Java moss grows EXTREMELY slow.
Anacharis grows about 1/2"-1" every 24 hours in my tanks.
For the anacharis, try to locate it in area where it's near the light, but not out in the open where the fish will mess with it too much. Corner is usually a good location.
Anacharis is always the first plant that my fish will tear to shreds when they're bored.
So far, good start.
Try to take pictures of your entire tank once every 1-2 weeks so you can monitor growth & treat for mineral deficiencies.