OK so I did a water change last night (20%) and changed my salt mix from kent to IO. Today the caps are looking very light two varieties are doing the same thing Everything else looks great. Fish seem happy. Nothing else changed. I am battling some cyano & diatoms, but that's been going on for awhile with no adverse effects to the corals. My digita looks marginally bleached too. These are the only SPS I have, everything else is zoas/mushrooms/kenya tree.

Could the salt change have caused this? Do you think it will work itself out?

check your params, are they the same as they were for your old salt mix? The softies you have are much less sensitive to change in params than your monti's will be.

too drastic a temp change can do that.

Sorry, I checked params right away. I'm at 8.2 ph, 0-0-0 as always (i'm running a sump full of cheato and chemi-pure elite). I don't know what the ph was before but can't imagine it was a huge change. I don't have a calc test.

My mag was low and my cap's were not happy, when I raised my mag they started doing way better. It could be many things, including temp

Now that's a possibility, my heater for my water change bucket broke and I pulled out a different one that didn't get it quite as warm (preset thermostat heater) and I also had to dilute it right before adding because the Specific Gravity was too high.

If that were the cause, will it fix itself? Looks like polyps are out, just the coloration is lighter.

Well I mean params as in Ca, Kh, Mg. Those are the important ones if you are keeping stony corals.

Guess I need to break down and get tests for MG and Calc. I have KH test, I'll run that later.

Yup. If your gonna get into SPS you should invest in the kits.

So any thoughts about the likelihood/timeframe of recovery? There is still color and they don't seem to be dead? Assuming it was a water temp thing how long does it take to recover from that?

This is the sh!tty part of reefing.... bad things can happen over night, and recovery can take months. If all your parameters are in line I would guess that you should see a full recovery in a month or so, hopefuly less.

my first guess would be temp change--monties seem to be really sensitive to that ime. but they're also hardy, they'll recover if everything else is ideal. may take a couple weeks, but it should happen.