I just want to make sure I'm understanding correctly - you're running your light 24/7...? If you are, that's not only bad for your plants, it's also VERY unhealthy for your livestock to have zero dark time.
It's very important to remember - no two tanks are the same. Even when everything seems to be identical, there will be variance. Adding water from one tank into the other just sets you up for cross contamination, as it sounds like you have some parasites showing up in one of your tanks. Milky white worms could be many things - detritus worms, planaria, rhabdocoela, etc., and the things zooming around could be something like copepods. While copepods are harmless and a good food source for small shrimp, planaria can bring havoc upon a shrimp tank.
I don't mean to sound rude, but it sounds like the tank that was doing well is thriving in spite of what you're doing. Testing and knowing parameters when you're having an issue is very important, and it's important for us to be able to even begin to try to help. Water movement for air exchange is very important as well - lack of air exchange can lead to problems like excess CO2 buildup, cyanobacteria, etc.. I'm also concerned about your CO2 setup. A plastic clamp to regulate gas output is very rudimentary and certainly not a good long term solution. There's zero ability to fine tune, I'm honestly surprised your shrimp are alive. I would suggest you stop injecting CO2 until you have a way to properly regulate it.
Information that will help us - dGH, dKH, pH, nutrient levels; what ferts, if any, you're dosing; ammonia and nitrite shouldn't be present since shrimp are alive, but knowing your nitrate level could help. Pictures would be helpful as well.