If people are immersed/involved, I hope you've Real confidence in your wiring... 50+VDC with any good ion carrying fluid means lethal power to someone closely connected to ground (50Vs' reference).
I'd check floating voltages (no pun), just to be sure nothing bad is happening. <<<)))
P.S. with 4 batteries, you won't have a problem. I'm cautioning about line powered supplies.
As limited time maybe check: **broken link removed**.
You'd have to split your lighting into 2 circuits, but also have more control.
I Googled "LED dimmer", took all of 30 sec.