How do you raise PH with Malaysian driftwood?

My pH has always been at 7.1 and now since I added these 2 medium pieces of driftwood my PH is now 6.5
I am building a DIY CO2 system this week and with this new drop in my PH level I am now worried.

What should I do?
25% water changes every few days?
How long will the PH keep dropping with this driftwood in my tank?
I heard I could use crushed coral, But I don't know how much I should use and when I would be able to stop using it?

My GH last tested 2 weeks ago was at 90mg / Liter is what they wrote down for me (whatever that means)

Nitrate 5
phosphate 0.3
PH was 7.1 like it always has been
Ammonia 0
Nitrite 0


A separate test from Petco using the Dip strip 2 weeks ago read
Hardness 75
Alkalinity 60
Details of my tank in my Sig
I will also be pulling out my EMP-400 and replacing it with a Fluval 1 Plus Filter