PH/KH low with GSP not looking so good

[Jackmot]

Hey!
So, I know this is not an urgent topic to deal wit but I would like to prevent any future emergencies haha.
I woke up today to find a bit of an algae outbreak and my GSP not looking too good (10-20% of the polyps not opened and those who are opened are not fully expanded). Naturally I did some tests and found the my PH was at 8.0 and my KH at 6.4.
Another "weird" stuff that has happened in my tank this past few weeks was an outbreak of dorvilleidae worms and one of my two turbos not being as active as it normally is.
I'm about to perform a water change in order to get those parameters back. Any other ideas??
Ammonia: 0 (API)
Nitrite: 0 (API)
Salinity: 1.024 - 1.025 (Refractometer)
dKh: 6.4 (Salifert)
Temp: 24.5-25.0ºc
Light: AI Prime 16HD
Refugium with Chaeto
1 Pulsing Xenia
1 Green Star Polyp
2 Mushrooms
2 Mexican Turbo Snails

 

[Jackmot]

Forgot to attach some pics haha, sorry.
The first one is BEFORE and the second one is THIS MORNING

 

[dwair]

8.0 PH isn’t bad. DKH is a little low. I would slowly try to bring it up if the water change doesn’t fix it. Don’t chase numbers hard

 

[Jackmot]

Yeah, probably I'm probably gonna do the water change tomorrow. If that doesn't help how would you bring it up?

 

[dwair]

Yeah, probably I'm probably gonna do the water change tomorrow. If that doesn't help how would you bring it up?

Slowly dose alk. Don't go crazy trying to raise it fast or you will create more problems for yourself. Like 0.5 dkh per day, slowly raise it up over a course of a week or so.

 

[Jackmot]

Slowly dose alk. Don't go crazy trying to raise it fast or you will create more problems for yourself. Like 0.5 dkh per day, slowly raise it up over a course of a week or so.

Exactly what I intended haha. Yesterday I did the water change and it went up to 7.0-7.4dKh but my GSP did not opened at all.
Today I bought the Aquaforest Kh buffer but i'm hesitant to add it because I dont have test kits for Mag or Calc.
Im still kinda newbie around the hobby haha, what do you think? should I add it?
Also, any idea of what could be consuming so much Kh? I've been noticing a lot of spirorbid worms lately, could that be it?

Thanks!!