Help, Whats wrong with my toadstool coral?

[Garbage_Island]

Hello,
I have had this neon green toadstool for over a decade. It doesn't do much growing and has been through some pretty neglected tanks during my college years. Recently it has started showing weird discoloration.
The only changes to my tank recently have been a treatment of chemiclean for some cyano, and I added a diffuser on my Radion (although that seems very unlikely to have caused this).
I have not added anything to my tank in well over 8 months except for an emerald crab (but this started happening prior to adding him). At first I thought it was just shedding but now I am concerned. When the lights come on he perks up and shows good polyp extension.
Any ideas?

 

[MixedFruitBasket]

If those spots are as white in person as they are in the picture (or more so) there is a very good chance that the chem clean or whatever you used cause it to lose zooxanthellae. However, you also say it perks up and shows polyp extension. It could just be that it's folding up for the night or deflating for the night more than it had been for whatever reason. If those whiteish spots are more yellow in person I would consider taking the coral out and giving in a iodine bath. Yellow spots can be a sign of yellow spot disease seen in toadstools.

 

[Garbage_Island]

If those spots are as white in person as they are in the picture (or more so) there is a very good chance that the chem clean or whatever you used cause it to lose zooxanthellae. However, you also say it perks up and shows polyp extension. It could just be that it's folding up for the night or deflating for the night more than it had been for whatever reason. If those whiteish spots are more yellow in person I would consider taking the coral out and giving in a iodine bath. Yellow spots can be a sign of yellow spot disease seen in toadstools.

Thank you for the reply!
The spots are extremely white, just as they appear in the photo. The flesh still seems alive (i.e. it does not look like it is dissolving or melting-- at least not yet anyway).
It's attached to a huge piece of rock, I wonder if I should still try to do an iodine bath.
Has chemiclean been known to cause issues like that? I didn't even use the full dose

 

[najer]

Has chemiclean been known to cause issues like that? I didn't even use the full dose

Yes, I used it once years ago, lost a big lobo and I only half dosed also.

 

[MixedFruitBasket]

Thank you for the reply!
The spots are extremely white, just as they appear in the photo. The flesh still seems alive (i.e. it does not look like it is dissolving or melting-- at least not yet anyway).
It's attached to a huge piece of rock, I wonder if I should still try to do an iodine bath.
Has chemiclean been known to cause issues like that? I didn't even use the full dose

It hasn't lost all its zoos. So they can repopulate as long as the flesh is healthy. At this point, I'd just watch it.

 

[Flippers4pups]

What's your water parameters like? I've kept leathers since the nineties.

 

[Garbage_Island]

What's your water parameters like? I've kept leathers since the nineties.

I know this isn't helpful but I honestly don't test water parameters. I usually can tell if something is wrong by the way the inhabitants look. Everyone else in the tank looks happy.
Im beginning to wonder if it was the chemiclean.

I did another 20% water change today. I am hoping that Mixedfruitbasket is correct and that the zoos will repopulate. I will keep my eye on it