Lobophyllia White Patches and Possibly Receding

[accel]

I have a Lobophyllia and I can't figure out by Googling why its edges are seemingly receding and there are white patches as if the skin is detoriating (at least that's how I interpret this)

It still takes food actively so I know it's still alive and kickin.

Photos:
https://ibb.co/f7KxES
https://ibb.co/iMzKTn
https://ibb.co/cbum8n
https://ibb.co/e43eTn

Params:
Ammonia, Nitrite, Nitrate: 0 using API test kit
Calcium: 440
Dkh: 9
Salinity: 1.025 using ATC Refractrometer
PAR readings: 60 to 80.
Waterflow: Enough to make a Hammer polyps to sway gently.
Vicinity: Montipora Capricornis and Feather Duster (this one is new so it has no bearing on this)
Temp: 78. 7 as of now
Fish: 1 Clownfish, 3 cardinal pajamas, 1 watchman goby
Inverts: 2 Skunks, 1 Fire Shrimp, bunch of snails
Tank: 40G with 20G sump.

I got this for free now and I want it to live. Other corals are doing fine (at least from what I see and have read online).

Anything I'm missing here? I don't see any pest unless I am not looking enough here.

 

[accel]

Update: PAR readings at max intensity is about 80 to 97

 

[Uncle99]

You say you have zero nitrate and phosphate. That will starve them.
Nitrate should be 2-5ppm, but not exceed 10 ppm
Phosphate should be .02-.04.

They need these nutrients to grow flesh, the Skelton comes from the calcification process

In essence, your water to TOO clean!

 

[accel]

You say you have zero nitrate and phosphate. That will starve them.
Nitrate should be 2-5ppm, but not exceed 10 ppm
Phosphate should be .02-.04.

They need these nutrients to grow flesh, the Skelton comes from the calcification process

In essence, your water to TOO clean!

I'd wish that's true. I kinda take this API test kit results with a grain of salt - based from what I have read online where people are not getting 100% accurate results. I ordered the Hanna test kits for another look and the Triton for a much accurate result.

The reason why I doubt I really have zero phosphate and nitrate is I see my chaeto and red ogo growing and I have some bad algae growing as well. My zoanthids have grown from 5 heads to 11 heads for the past two weeks I think.Some of my encrusting corals have encrusted their plugs (not dramatically though)

On a differenr note, I dipped the Lobo in an Iodine solution based on the product's directions. I can see the swelling of the white parts have lessen and as soon as I dropped the Lobo to my DT his 4 inches tentacles suddenly started stinging nearby corals as if he got mad for being pulled out.

I am still observing him. I am a heavy feeder so I really doubt I have zero Phosphates and Nitrates although the test shows i have zero (the visual chart is very tricky). One of the stuff I feed my corals is the Reed Roids which has a notorious side effect of spiking the water with nitrates and phosphates (if I remember).

I feed phyto in the morning and evening everyday. I feed mysis, hikari pellets, and ocean nutrition pellets a lot for the fishes every day as well. I give reef roids 3x to 4x per week.

 

[Tripod1404]

Its losing color (or bleaching) there seem to be some tissue recession as well. White patches are skeleton being visible under bleaching tissue that lost color. You can see the septa under the bleached tissue. It might be normal, lobos generally bleach very easily with changing light conditions. Tissue recession is more worrying though, it generally indicates issues with water parameters.