What's wrong with my hammer?

[avocadoman]

Two of my 3 hammers seem to be losing polyps. Are they sick? Is this a disease, or maybe my little emerald crab, or something else?

Parameters:
pH 8
Alk 8.5
Ca 425
Nitrate 0.3 (was 0 for possibly up to a week, I added some nitrates after I saw that)
Phos .06
Mg 1300

I maintain levels with All For Reef and everything besides nitrate and phos have been very stable for months.

 

[ReefStable]

My first thought is something bacterial. I would do an iodine dip, and maybe a Bayer dip just in case of pests. Cipro might be a good idea as well.

https://reefstable.com/blog/how-to-dip-coral

 

[Pistondog]

My euphyllia like nitrates above 3ppm. We dose ammonia.