Questions - Need some input

We got home from dinner tonight and found the tank full of small particles and a haze. They are dark green, about the size of a 'normal' freckle, and dissolve/smoosh without feeling them smoosh in your fingers.

I did a water change today(the first in a few months...I know). Inhabitants now consist of 2 clowns, 1 sailfin tang, 1 green chromis, 3 clams, zoas, ricordea, GSP, 2 BTA, 1 cleaner shrimp, various snails(who have been egg laying), a few emerald crabs, some Anthelia, fuge ...