I agree with the acan on the first one (echinata/subechinata most likely). Hard to tell on #2, but cabbage is one probably close. Third and fourth I'd say are Paly's. They look like ticked off button polyps (generally green in the center).
As Markus was saying, phosphates can bind to rock and sand over time, then leach out back into the tank. Some run PO4 reactors, etc., but anything that strips water of something quickly can be a problem. I run pickling lime in my top off water to help the skimmer pull the PO4 out. This has several caveats, though. You can quickly spike your pH doing this if you aren't careful.
1)-only use pickling lime (kalkwasser) in ato if you have a float switch to control the top off. Otherwise, you may put too much in at once.
2)-don't let the ato reservoir run dry with precipitated pickling lime in the bottom. You'll pump large quantities of the precipitant in, spiking pH.
3)-don't breathe in the fumes when mixing the pickling lime and RO water.
In moderation it is working well for me. I have the occasional spike of pH when I do something stupid, but my system is a little over 800 gallons, so it does okay even with my screw ups.
As long as your parameters are in check and you have at least med flow and decent lighting, they should recover. Just give them some time and remember nothing good happens fast

. I'm a fan of runnnig carbon 24/7 (generally extruded carbon pellets instead of the lignite-rocks of carbon). Rinse it well before use to remove the dust. That help strip out chemicals that unhappy corals might be putting out. Carbon can also strip the water quickly, so if not already running it, start with a small amount and work your way up. There are some carbon calculators on RC, I think. I think most run just a few cups for smaller systems (100 gallons or less?). Let the acan get some flow, but not a lot. Once the septa show through, algae starts growing and grows much faster than the coral can recover in many cases. Once algae is on the septa, you'll usually have some skeleton spots... Lower flow seems to get acans and many other LPS to fluff up, which is why I'm suggesting the moderate subdued flow for that guy (nothing likes being blasted directly, though).