Can I dose a little Soda Ash?

[Court_Appointed_Hypeman]

5 weeks old tank 75g with 18g vollume in sump.

Current values
Temp 78.5 (2 probes)
Ph 7.96 probe, (re calibrated twice today after a crash that recalibration verified was real)
Nitrate 1 PPM (nyos)
Phosphate .03 PPM (hannah ulr)
Salinity 1.025 SG (calibrated refractometer)
Alk 7m6 DKH (hannah)
Calc 460 (red sea)
Mag 1440 (aqua forest)

Today, around 11AM my PH started crashing to 7.48 and it freaked me out a little, even though its cold we turned on the house fan and opened the windows and turned over the air for a while. It went up to 7.7 and slowly climbed up to 7.9

Usually low is 7.9, high is 8.2. The last 2 weeks its been between 8.09 and 8.22 on its daily shifts.

My DKH has dropped from 1 week ago, and I was wondering if I could kick it up some.

Inhabitants:
2 clowns
1 CBS
4 Turbo snails
1 trochus
3 ceriths
2 hermits
2 astrea
1 chaeto that finally doubled in size in one week. Was a golfball 4 weeks ago, now a softball.

Lots of diatoms that are starting to disappear
And tisbee pods and dosing phyto

Thanks!

 

[Court_Appointed_Hypeman]

We have a very full house, 5 kids 1 wife, 2 dogs 1 cat, 8 tanks. I know my carbonic acid levels will be higher, but we have been shutting the house lately and this dip was the first of its kind. I am new to saltwater so i know i might be being a baby. But i have coraline algae starting and i dont want ph to get so low it inhibits it.

 

[Randy Holmes-Farley]

I'm not sure the pH is accurate, but if you are already at 7.6 dKH, adding soda ash to boost alk and pH will soon run out of capacity to boost pH before alk gets undesirably high.

It's certainly fine to add some, but looking to other pH measures may also be desirable.