I agree with the other posts pointing at 0 nitrates being a possible cause for some of the algae allowing the algae to potentially outcompete the corals. From my understanding 0 nitrates is good only if you have 0 phosphates as well.
For the algae, what I've found in the past is iron in the water. Certain algaes (especially hair algaes) will grow like CRAZY when there's iron present for them to feed on, and then they'll strip the nitrates from the water.
Any rusty magnets or metal pieces? I believe
@Imrahilwjz found his return pump as a most likely source for copper and other metals in his tank. I had a magnetic glass scraper that rusted and caused a massive amount of GHA growth that I couldn't get rid of until I pulled the rusty magnet out of the tank.
For Dinos, I recently beat those back with MB7, live Nitrifying Bacteria, a filter floss pad in the tank, and UV. Took about 2 weeks of that and getting my phosphates back up above 0 and the Dinos disappeared.
The green slime could be a bacterial blooms as well. If you're having invert and livestock deaths, there could definitely be some ammonia spikes causing a bloom of bacteria trying to consume that.
Also, MB7 lowers Nitrates so you might have to use more NeoNitro to get above 0. What dose MB7 are you using and how often?