Noob needs help

[PunkKid]

Alright so here's the situation. I currently have a 30gal tank up and running, its 4 months in. And I've started introducing fish, invertabates, and soft coral.

2 main issues.

1) My clown fish now have brown spots all over them. Looks internal, they dont have any bumps. Also they seem to have seizures every now and again.

2) I had a pulsating xenia and a Mushroom acan or frag. Anyways, they were doing really well. Then after I did a water change, they shriveled up and died off.
I did some water testing and everything checked out.
Did another test today. And water is as posted.

ph-8
salinity-1.026
Nitrite-0
nitrate-80-100
ammonia-0

Im concerned the fish may have been infected with trematode's. But I have also been told it could be a pigment change due to the lights being turned on too fast or flickering??
Stumped as to the corals though.