Euphyllia question. Normal or not?

[Beck]

My tanks pretty established and I have quite a few different euphyllias, but every once in a while a few heads of a colony will just start dying off. Always receding from the bottom. Soon as it gets up to the ribs it dies fast. Never seen any pests, or anything picking on them. The only thing weird I've noticed is sometimes right under the flesh on the skeleton it has some pink or red, but not always.

Is it normal to lose a few every once in a while?

 

[xxkenny90xx]

That doesn't seem normal. What are your parameters and more importantly how stable have they been?

 

[shakygator]

I've only seen them die off when they get shaded by new growth or try to grow in a bad direction.

 

[Coral therapy]

I have had the same pink show up under receding flesh of brains.

 

[Beck]

That doesn't seem normal. What are your parameters and more importantly how stable have they been?

My parameters are really stable. I have ATO, and a DOS adding 2 part. Temps controlled with a inkbird running a heater, and a fan.

Salinity 35 ppt
Temp 77 - 78.5
Cal 440
Alk 9
Mag 1350
Ph 8.2 - 8.3
No3 0 (I've tried getting it higher with no luck)
Po4 0 (same I can't get it to even read)

I also just ordered a triton test just to double check everything.

 

[Beck]

Update.
Still trying to figure this out I sent out a Triton test and it came back with really high iodine. I started dosing brightwell lugol a few months ago when I was reading zoanthids need iodine. Just going off the directions on the bottle I thought I was fine. Lesson learned, never dose anything you're not testing for.