Couple corals not doing so well

[Jake_the_reefer]

I just got home from work and 2 of my corals are not looking good at all, my sunkist bounce mushroom and purple hammer are not looking happy what so ever while all my other corals look happy as can be.
Could it be an emerald crab? I just saw him picking at my gsp so it's all retracted. I also changed the flow up last night so I have a new deadzone in my tank that has diatoms
Ammonia 0
Nitrite 0
Nitrate 15 (fighting to lower it)
Alk 9
Calcium 425
Salinity 1.023(had a dip a couple weeks ago, slowly raising it)
Temp 78.3

 

[Brad Miller]

If the emerald crab doesn’t have enough algae to eat, he will turn on your coral

 

[Jake_the_reefer]

If the emerald crab doesn’t have enough algae to eat, he will turn on your coral

To add more danger it's a very large male... and yeah the snails stripped the rocks of algae.

 

[vetteguy53081]

When was last water test?
What is salinity?
Bump up whites about 5%.
Have you fed either one recently?

 

[Jake_the_reefer]

When was last water test?
What is salinity?
Bump up whites about 5%.
Have you fed either one recently?

I fed the corals last night and readings are from right before this post.
Salinity 1.023 due to a drop a few weeks ago. Trying to get it up

 

[vetteguy53081]

I fed the corals last night and readings are from right before this post.
Salinity 1.023 due to a drop a few weeks ago. Trying to get it up

Salinity quite low.

 

[Jake_the_reefer]

Salinity quite low.

I was wrong. Its 1.0245

 

[Jake_the_reefer]

I'm going to do a 15% change in 1.0257 salinity water

 

[Jake_the_reefer]

I think it is the crab. Both corals look a lot better

 

[Hemmdog]

What’s your phosphate level.

 

[Jake_the_reefer]

Looks like around .06

 

[FacebookJail]

All of the parameters you posted are great (provided they are accurate), that small discrepancy in SG should be of little worry. 15ppm nitrates are fine. As mentioned above I'd suspect some type of pathogen or critter at fault.