Your PH at 7.0 is fine for a soil grow. Next time you mix up your soil mix, include a SMALL handful of Granulated Dolimite Lime per two gallons of soil into the mix. It will stablize the PH throughout the grow.
Keep in mind that the lower figures for PH ... say between 5.2 and 5.8 are intended for hydro solution applications and not for soil grows.
Vi