Kh/Alk boost?

[Ab129]

So after ich wiped out all but one of my fish, my DT has been sitting fishless for 38 days. During this time I have continued dosing vinegar and feeding my few corals several times a week.
About a week ago I noticed my hammer coral stopped opening up as large as usual. Color still looks fine but he is staying kinda small.
I checked my parameters to see where I’m at and these are my numbers.
SG. 1.025
Nitrates 5 ppm
Magnesium. 1320
Calcium 390
Ph 8.4
Kh/Alk. 6.4
The only number that looks significantly out of whack seems to be kh/Alk
Could this be the cause of my corals behavior and how can I increase to a suitable level.
I was going to get the salifert kh ph buffer but can’t find it online.

[Sk8r]

That's weird. I use Kent buffer, always has worked for me. Bring that cal up to 420, while you're at it. Test multiple times per week until you get this stabilized. Also check your expiry dates on the tests. A wrong test is possible. But yes, that low an alk could account for many things from fish aggro to corals tucking in.

[nereefpat]

Kh/Alk. 6.4
The only number that looks significantly out of whack seems to be kh/Alk
Could this be the cause of my corals behavior and how can I increase to a suitable level.
I was going to get the salifert kh ph buffer but can’t find it online.

Yes, an alk reading in the sixes can cause trouble with corals.

Just use baking soda (not baking powder) to bring it up. Don't increase more than about 0.5 dKH a day.

[Ab129]

I was thinking the fact that I have not been doing water changes since I’m fishless the last 5 weeks might have something to do with it so I did a %15 water change and retested and the Alk had increased to 7.0.
I will see where I’m at after a few more weekly water changes.