Need help corals are dying!

[justin350z]

Hey guys a little upset with my tank right now. It's been going for over 4 years and I have just started battling red algea. I leave for a couple of days and come back to my SPS corals dying. Frog spawn and birdsnest are fine. I don't know what to do? All of my Nitrate, Alk, and PH are fine. I haven't done anything different. Here is some pictures... Any help will be wonderful.

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[weaglereefer]

If you need a second set of kits for reference let me know.

 

[smoothie]

Check your temp too. I've been reading more about these outbreaks starting out in cold weather. Don't know if there is any relation besides bacteria dying off

 

[spike]

Any chance of a temperature swing due to colder temp we have been experiencing lately?