I don't see any evidence of dinoflaggelates in any of your photos - so I don't know why you're going down that path. And 6dkh isn't killing anything.I'm shocked by the killing capacity of these little gnats. How in the world can they destroy a tank in the span of 2 days? I'm just about back to square 1 with losses, only a few fish left alive that I could find. I may take this opportunity to phase out a little bit, maybe downgrade. I'm done paying for re-starts that I didn't even cause, it's very discouraging.
Did you do anything to the tank yesterday or the day before? Anything happen in your house? Any cleaning? Etc