Ph level in soil increases itself

[kaujinieks]

Hi,
ph level in soil increases itself to 8.0 and i can't lower it.

Run of water ph7.8
After flushing soil ph and run of 6.7 .
2 days late ph 8.0 in soil and run of 7.6.

Soil: Bio Bizz all-mix
Nuts:Bio Bizz grow
Ph down:Canna Organo acid

Any advices, please!