Is this normal for a montipora?

[EVandh2o]

I've only been in the hobby for about 6 months. I got this montipora a couple months ago and this morning I noticed the white areas at the base. I don't know if this was there from the start or not. Is this something I should be concerned about and if so what can I do for this coral? Thank You.

 

[RedReefer]

Not normal. It's receding. Any recent water issues. Did you change anything? Like lighting, water change schedule, salt. Might also try dip and see if any pest fall off

 

[exnisstech]

When that happens to my SPS it usually continues until the entire piece is gone. I've heard it suggested to cut the dead part of and reattach the live frag but that has not worked for me. Hopefully someone with more positive input will stop by.
I may be wrong but it looks like possible RTN or STN and it's one of the things that happen with SPS that no one has figured out the exact cause TMK.

 

[Mr. Mojo Rising]

I would cut off that big branch at the top while it still looks healthy, otherwise you will probably lose the whole thing. I've never seen it stop once it starts.

 

[exnisstech]

There's always hope. I had forgotten about this one but it was dying top down vs bottom up.

 

[EVandh2o]

Not normal. It's receding. Any recent water issues. Did you change anything? Like lighting, water change schedule, salt. Might also try dip and see if any pest fall off

About 2 to 3 weeks ago I changed salt brands from Instant Ocean to Tropic Marin. I think I got about 2 water changes in to the Tropic Marin now.
I did have some fish die a few weeks go. I thought they may have had flukes, so I medicated the tank with Prazipro for 3 weeks. Remaining fish at the moment seems very healthy again.
Parameters seem good to me and they have been very consistent so far.
KH- 9 to 10
Phos- .25 I know it's high, but it has been .25 every week for the past 6 months. LFS said if consistent it's fine as well.
Nitrate- 5.0 consistent. I know it's high I feed way to heavy, I'm working on cutting back. But again it's consistent.
Calcium - 400's with instant Ocean. I just notice it is in the 450 to 520 range with Tropic Marin. Could this cause an issue?
Salinity- 1.026 or 35 ppm
Thanks again for the assistance. I hate to see this happen to the coral and I want to give it the best chance to live.

 

[X-37B]

I've only been in the hobby for about 6 months. I got this montipora a couple months ago and this morning I noticed the white areas at the base. I don't know if this was there from the start or not. Is this something I should be concerned about and if so what can I do for this coral? Thank You.

Hard to tell whats going on in that pic. Definate recession. Check closley in the morning before lights come on with a flashlight.
Look for a white nudibranch. Eggs may have come in on the frag and now they hatched and are eating the monti.
I have had them before and the damage looks similar.

 

[Mr. Mojo Rising]

What test kits are you using? Those look like API numbers? The API phosphate test is the worst.

Changing salts is very hard on corals. I've tried to change on my reef tanks and my corals reacted so badly I had to go back to the original brand. My guess would be the salt change, but its just a guess, there's really no way to know for sure unfortunately.