Several things come to mind.
The first one involves the beer. How many of those do you dose in a day lol?
Now on a more serious note.
You're using GFO fairly aggressively, it seems, and also have very low phosphate according to the numbers you post.
That's generally good for SPS, but they do need "some" phosphorus.
In your case I'd recommend reducing your GFO by half, and increase your direct coral feedings using a very fine particulate food like Reef Chili or something.
You don't want to "jack up" your phosphate readings, but you do want to sneak a little in there for nutrition....
The corals just sound starved to me, limited by phosphorus. They don't need much... just a little.
Just to throw this out in the open, but I personally believe that grounding probes aren't as useful as people think.
I won't fully claim to understand all that's behind this, but I do know for sure that a grounding probe will turn stray voltage into stray amperage (current), which is probably more of a problem than stray voltage.
I have around 10v "stray" in my tank and I totally ignore it. It's coming from my Maxi-jets (I have 4 or 5 of them in the system) and maybe some other pumps, and it goes away little by little as I turn them off one by one. So I know it's not a single "leaky" pump.
I just ignore it. Voltage by itself isn't dangerous, it means there is "potential" danger. Current, however, is very dangerous (well, depending on the load). I know on my system, a latent 10v isn't anything to worry about.