If your tank is cycling, it's actually better for the pH to be giving higher readings. If it drops below 7, the growth of your bacterial colonies will slow and in some cases, can even go dormant.
If you do want to gradually lower your pH, you can use wood in your tank hardscape. The tannins released will slightly acidify the water and drop the pH. Likewise, Ketapang leaves or the addition of peat in your filter, will also give you similar results.
One of my tanks has an extremely high pH reading because I put in some crushed coral to buffer the pH up (it was stalling my cycle), and forgot to take it out. However, the betta living in there is perfectly fine, and I haven't noticed any ill-effects from not having the 'perfect' pH.
Whenever I do water changes on established tanks that have a very different pH from my source water (example my Betta coccina tanks sits around 5.0) I usually only do 25% or so water changes so as not to cause huge shifts in pH.