Usually my next plan, if a uv doesn't work on a particular species, is to start bacteria cocktails in an attempt to add competition. I like pns proobio and Dr Tim's eco balance/waste away. A hearty mix of (non tigrio) copepods possibly live phyto may add some predation. The next option that I would consider would be adding real ocean live sand to try and get other zooplankton. Again, dinos are not well understood as a phenomena in thks hobby as you probably have seen, and at most someone can do is recommended things to try that may or may not have been related to their dinos going away.
Ps don't forget to double check your test kits is possible. I don't think they are off but it's always something to consider.