My ph is sitting at 7.3. In the last week I have changed the water 20-25% 3 times and once a week for 3 weeks before that at 10% change. Now water started with tap but all water changes have been with RO @ 6.2. Is this just going to take time to lower ph or is it possible that my “Siri” stone is raising ph. My tank is a 20 gal with a mixture of fluorite and stratum. Tank has been up for almost 3 months with CO2 and about as many plants as I can fit.