the shrimp may become lunch as well as the plants.you will need to do large water changes once a week.
your goldies probably did not get to their potential of 8" long because they were in an overstocked tank.they put off growth hormones that will stunt
Try pulling everyone out, re-arrange the tank a bit, then add them all back in. This should break up any established territories and put everyone on equal
Do you clean the substrate? I've found that even with lots of water movement, most waste ends up in the substrate. The filters get clogged with mulm more
Regarding the use of Betta Revive: It's best if you're doing water changes, but no need to do 100% water changes. They instructions say that it will