Coral health

[ThorEffex]

In the past couple days my doser messed up and alkalinity fell to 6.1 and my some of the sps in my tank started to show these white string like things from their flesh, not their polyps.

Another coral has a TN around the base of it and it is moving lowly through the bottom of the branches. It has been dipped 3 times and I do not see any critters on it and it gets a little worse everyday. I think the first 2 might have an issue with the alkalinity swing.

This one is weird it looks like I have some kinda crab living under it but I don't see any crab and I've pulled it out dipped it and pulled out the magnifying glass to look at it but it keeps me guessing.

Any tips or advice would be appreciated

So a bit about the tank and it's parameters. It's a 60 gallon system about 7 months old being doesed with 2 part bionic, ATO waters is rodi 0 tds.
Phosphates and nitrates are undetectable
Calcium 420
Kh 7.2 (trying to get it back to 8-9 .4ish per day)
Mg is 1350

 

[Allmost]

Any other changes recently ?
Do a larger than normal water change ... Always helps get the chemistry back inline, while u slowly increase kh. 6 isn't that alarming, but the rapid change from 9 could have been.

I see ure from Toronto too, any blackouts ?

 

[ThorEffex]

Nope I'm lucky I did not lose power a lot of destroyed trees everywhere, I hope your power didn't go out either. No recent changes for the last 2 months. It was dropping at .6 kh per day. I didn't catch it till the second day of testing after increasing the doeser and it dropped another .6 kh. I'll try doing a water change tomorrow morning as the lights are about to go off.