Coral dying

[ReefWife]

Hi everyone. I'm new here. My husband has a 75gallon reef tank. It was thriving with fish and coral for a few years. Late last year... Maybe around sept or October. All of the corals began to die. We cannot get any to stay alive. All fish are fine. When he tests his water or takes a sample to get tested... Everything comes back fine. So now we just have fish with plain live rock. Does anyone know what could be the problem? Could it be lighting? These lights obviously did the job for the last few years but maybe time to replace? Or could there be something else wrong. I really miss all the colors of the corals in the tank. I was wanting to get him a pair of clowns and an anemone as a gift (besides the fact of wanting to get it full of coral again) but don't want to do it just to have the poor anemone die.
Sorry for not having more technical info. I'm just the wife

Thanks for any help.

 

[ReefWife]

I should add that crabs/snails/etc are doing fine as well.

 

[Sniperhank]

Welcome!
In terms of trying to help out, can you tell us more about the tank? What kind of lighting is above the tank? What exactly are the parameters, as 'fine' doesn't tell us much in terms of diagnosing what is going on. What kind of coral are we talking about, softies? LPS? SPS? How often are water changes done? Has there been any increase of algae growth in the tank?
The more info you give us, the better help we can be.

 

[ReefWife]

I will get all that info for you when he gets home from work. Just recently there seems to be an increase in a purple-ish/red algae. But that's just very recently. Also there seems to have been a very large (and annoying) outbreak of tiny white starfish type critters all over the glass and rocks. I can't recall how long ago that began... If it was before/during/after we lost all of the coral, I'm not sure.
Corals we had for years that suddenly died (that I can remember the name of at least):
Frogspawn
Candy coral? Torch coral? (Is that the same thing)
Variety of zoas
Mushroom polyps
Something that looked like pink trees(sorry!)
Star polyps

 

[ReefWife]

There is only 1 type of coral that has survived whatever happened/is happening. There are 2 of them in the tank. Will take a pic of it as soon as my phone charges.

 

[Sniperhank]

Ok, so basically soft and LPS corals. The small starfish you see are astera starfish. There are rumors out there that they will eat coral, but I don't buy in. Any member of a clean up crew can go rogue...but rarely and is usually just cleaning a dying coral up. It is their job afterall.
But in general, it is typical to see atleast one outbreak of astera stars during the life of a tank. After several years running now, I have one just beginning as we speak. They'll eventually die back down and aren't anything to worry about.
In terms of the red/purple-ish algae...is it really slimy and can be blown around the tank? If so, this is cyano bacteria. A sign of nutrient issues in the water column.