A few updates. My dad, who is 95, had a fall and broke his pelvis. A week prior to that I took on a small project. So life obviously became a bit more complicated and time for the tank greatly reduced. As a result, I was paying much less attention to the tank other than to check the ATO and supplement vessels for levels, feed the fish twice daily and clean the skimmer once. However I was seeing much more green growth on the glass, but didn't have the time to look into it beyond a few quick tests of nutrients. Tests didn't show any appreciable changes other than a slight rise in NO3 to between 5 and 10ppm - normally runs at 2ppm with no issues. PO4 was still almost undetectable at .03 LR Hanna.
A few days ago I had some time to look into things further and found that the dosing vessel and the line feeding the tank for vinegar was gummed up with what I guess was bacteria, preventing normal flow from the dosing pump. I never really thought about the idea that bacteria would grow in the dosing vessel and attached tubing, but I found that the cap to the dosing vessel was not screwed on tightly, so this might be the contributing factor to allowing bacteria to grow. After cleaning, refilling, tightening the cap

and allowing it to run the dosing schedule as usual, things have cleared up and are back to normal.
I only bring this up to make others aware that even if we believe we have a plug and play system, things can and will change or go wrong so everything must be checked for propoer operation on a regular basis.
The other update is ............ I lost a fish - yellowtail blenny

There's no disease in the tank that I can see. The blenny and all fish have been eating well and look bright and colorful. However the blenny has disappeared. The only thing I can think of is some other animal in the tank ate him. To my knowledge, there's nothing that I introduced that could do that. My only guess is, an emerald crab. There are three in the tank, but one is larger than the other two. Do emerald crabs attack sleeping fish? The blenny used to find a hole in a rock to hide and sleep.