Here is my two cents worth. Maybe 10 cents worth.
I've succefully kept everything except SPS pretty well for over two decades.
BUT I've done everything wrong with SPS for a few years, so I'm an expert on what NOT to do.
Over last two years, I've learned a lot, and finally got SPS to do very VERY Well.
I would say these are the key things that got me going well... (#0, is probably my turning point toward success)
0) Stop any additives (other than Alk,Mag,Cal dosing as needed). That means STOP corals foods, Aminos, Ramp down (not stop) Carbon Dosing.......(Fish food is mandatory (variety), and optional supplimental BACTERIA like Zeobak)
--- Additives may work short term, but in the long run lead to problems and side effects, if you are not dead on.
1) Don't worry about the CYANO (at this point). It's harmless to fish and corals, and once things are back to normal in your tank Cyano will go away. You will have a choice at that point to make improvements to help it go away faster.
At this point FOCUS on things that are harmful to your Tank System, Corals and Fish.
2) Focus to be 100% sure your got rid of the red bugs. To succeed with your SPS you need to ensure that even if you stablize your Tank/Water Parameters, Nutrients, etc, that they don't come back to ruin the Party.
3) Damaged Corals are Hard to Save. Even if possible it will take Months, so don't focus on them. Consider them a loss (worst case) and FOCUS ON THE HEALTHY SPS. That will help you keep a positive mind, and not mess things up more, trying to save what you can't. (For me it helped to move the bad sps somewhere at back or out of view, and just hope they make it)
5) Get your Nutrients up. Naturally (which mean fish poo, made by a nice quantity of Fish that fits in your tank).
--> You may want to get more fish, or just feed fish more often, but don't over feed to create waste that goes down your sump.
--> I've never played with Turning Skimmer off (periodically) since I believe that Constant Nutrient IMPORT and EXPORT was best.
I put #5 above #4 to make a point. They go hand in hand for success. And it key to get your Nitrates/Phosphates up.
Then you'll be able to control how you want them lowered and stable.
4) The next Most imporant thing is STABILITY. Don't chase numbers, but get stable #'s (within a RANGE)
---> For SPS, ALK is probably the most important one. (In my case unstable Alk was the SPS killer, Damager)
---> Once you get ALK stable, Calcium and Magnesium will follow nicely (ie by a Two Part Dose, or Water Changes)
---> However Phosphate swings can even be worse, especially a drastic drop (like too much GFO at once)
---> For me various combos of Nitrate and Phosphate worked, (find your tanks Natural and get N&P stable)
-------------- > I found that Phosphate=0.05-0.15 is best (0.1 is middle best, and even as high as 0.2, but not any higher)
--------------------> (I achieved this by proper # of fish, and feeding often, the got it down and stable by small amount of GFO, slow trickle, and changed like clockwork every 2 weeks)
--------------------> You may not need GFO, but it was the only thing that worked for me with my Fish load.
--------------------> Use Floss, not too much Carbon to polish tank water. I like ChemiPure Carbon Resin (the basic version)
--------------------> I also never run SOCKS full time, just use them Briefly when Power Washing Rocks from Detritus.
-------------- and N doesn't matter that much, but too high will fuel Cyano, and Algae Blooms.
--------------------------> So the best Range I found is for Nitrate is between 1ppm and 5ppm (but you can go higher)
6) Your Water Changes, Lighting, Flow, Coral Placement, Filtration are just common sense stuff that varies between each tank setuup. Plenty of resources out the to get those thing right (PAR Meter for Lighting,etc)
6b) For me one piece of filtration I would never give up besides my Skimmer is my Cheato Grower (ATS) in my Sump. You can have some control over N&P since you can increase/decrease PHoto Period, and it bring up your PH and Oxygen levels at night when your DT lights are off... (Unlike Carbon Dosing products which get your tank hooked and must be weaned off)
7) If you suspect a problem like too high levels of toxins like Heavy Metals metals, consider a ICP test so you can fix the issue with a Heavy metal remover (ie Cuprisorb), or sleep peacefully knowing you don't have something causing your SPS issues.
8) I had years of issues with CYANO (even in my NON SPS tanks) and it all ended after I removed my Sand Beds and went Glass bottom. I was just too lazy to keep cleaning the Sand. I miss the white look from years ago, but Coraline bottom is pretty too.
10) I skipped (9) since 10 is a nice number. Stop doing what others FOLKS tell you what to change, or do. They will mess you up (not intentially), without the knowlege of all the details of you setup, routines, etc.
Listening is fine. Seek knowledge, not Quick-Hit, Miracle-Cure Advice.
Pick up successful tips, tricks, observe good running setups, and apply your own methods to your own chosen target/ranges.
Then get organized (log everything). And be consistant in your maintenance, testing, and minor adjustments. All SLOW CHANGE, with patient observations till next change.
I think it's way more important to listen to what Folks say to "NOT TO DO", than what they say TO DO, or CHANGE for improvements!!
(Many of the things I mention above, are illustrated in my two Tank Threads Links in my signature Below )
[ Gensis I is all the Struggles with SPS. Killing them slowly or quickly for two painful years. But I learned a lot. ]
[ Gensis II is where I finally got SPS right...with help from more DIY automation, but the fundamentals are the same if done Manually]
AND LAST BUT NOT LEAST. As much as folks say they have SPS without effort/skill in young-tanks, or as much as you see people having beautiful SPS colonies in Georgious Inspirational Tanks. SPS are tough to keep. So easy to upset them. One mistake and poof. I didn't give up, but I lost a ton of SPS Frags trying. Maybe start with easier/less-expensive to gain the skills to keep them alive and healthy, then move up to more difficult and prized specimens.
Hope this helps.