Hi Lexy,
Yeah, the problem with gases in water is that they immediately try to escape from the water as you can see by the bubbles. It should be clear to you that the bubbles are moving away from the plants, not moving down into the plant beds, right? Barr estimates that about 90% of the gas we inject immediately dissipates into the atmosphere, so we really have to find a way to force that remaining 10% down and to make contact with the leaf. The hardscape and other objects have a powerful impact on flow and distribution and unfortunately, it's not possible to predict, so this forces us to experiment with the arrangement. I cant recall whether you are adding liquid carbon daily, but if not, you will see improvements by doing so.
You can spread out the stems over a wider area to reduce the blocking. I know it's frustrating after all the energy, but I always try to discourage people from just ripping out the plants that are not doing well, because one has to learn how to solve the riddle of their tank. Changing to a different plant does not always solve the root cause. When you learn how to solve the problem, that lesson stays with you and helps you to recognize and solve future problems. I've seen so many cases where people have a lot of problems and they get frustrated and they drain the tank, rip out all the plants and start all over again...but they haven't changed. They didn't learn why they had a problem and so make the same mistakes the second time, so the same problems return.
You can even try extreme maneuvers such as placing the long spraybar at the bottom front glass pointing towards the back, just to get flow down at the bottom and to see what difference it makes. YOu can even rearrange the hardscap to see what effects there are. It doesn't have to look pretty right now because you are trying to understand the problem. That's another thing that stops people from being creative problem solvers, they don't want to mess up the arrangement, or to have piping in areas that diminish the aesthetics, but, dying plants also ruin the aesthetics, so we need to figure out and visualize the problem. Once we see an improvement in the plant growth, then we can find a different, more aesthetic way to get the same effect.
Cheers,