I have a 15 gal and a 10 gal, all the levels are good, in both the nitrite and ammonia are 0, nirtate is 10, but there has been a swing in water PH in both tanks. About a week ago I noticed a rise in PH from 7 to 7.2, and alkalinity went from 80 to 40, and the water was hard, now it's soft. I...