get more fish. get up to 8 or so. Don't add them at once. get 1 maybe every 2 weeks and test. As long as your ammonia and nitrates don't spike, add the next fish. If you get a spike, do a water change and add some Dr Tims in ( the smallest bottle will be enough) to boost the bacteria.lol @ your skimmer. I think my bioload is just too low with the 4 fish to support the corals (and the algae). I have it running just for gas exchange now, its not collecting anything into the cup. Even after 4 days of it not collecting anything, nitrates and phosphates are still bottomed out.
There was a bit of cyano when I got home from Nashville today (my wife warned me). I blew it off everything and changed my reef diaper. On the bright side, the GHA is basically gone so I'm guessing it is releasing phosphates and I have no nitrates so it is just out of whack. My guess is that nitrates had been down for so long the bacteria wasn't able to uptake anything and the algae was outcompeting and now it is out of phosphates and the GHA is giving them up to the cyano. I picked up NeoNitro and dosed 3ppm today, I'll test again tomorrow and see if it budged. I'll dial in a dose to keep around 5ppm and then adjust based off readings. Should be back to stable shortly. I'm even starting to see the first spots of coralline.
I'm trying to decide if it is wise to add more fish yet. Tailspot is on my list, and bioload seems to be going in the right direction considering I'm too high on consumers... decisions decisions. Maybe I'll check out the LFS this weekend and flip a coin. I still haven't dosed any algaecides, reef flux, or razor. Next weekend the torch and scolly come in. I probably should just so the corals have some N and P to consume.
Obviously test for your other stuff, but try to leave the tank alone and let it get stable. Don't chase parameters too much. If your off on your calc or mag a little, do a small dose, but don't chase it. That kind of stuff.
But I would hold off on more corals until you can get that steady 8-10 fish so that you have a source of nitrates.
Oh I also started doing water changes every other week (assuming everything was good) so that I could let my nitrates stay a bit higher.