Changed over to ADA and have question re PH

Last week I changed over to ADA Aquasoil.
I noticed a drop in my ph right away, about a full point.
Tom after a few days I took a sample of water and let it sit out for 24 hours.
It read 6.2 on my Pinpoint monitor. So as per your advice I set out to drop my PH by a full point, at 5.3 my fish were doing somersaults and gasping. Almost lost a few. Put an air stone in the tank and brought it dack up to 5.7. They are much happier.
The question is is that enough CO2?
How does the ADA soil affect the CO2 carrying capacity of the water?
Is there anything I should be doing?

My water here in Vancouver is extremely soft. Practicaly 0CH - 0KH
I have added some Calcium carbonate and epsom salts to help buffer the water.
What do you recomend I shoot for with my KH and CH and PH????