Yeah man. Once you add your nutes you're then able to change the pH without it fluctuating like crazy. If you're thinking of flushing with the R.O too, then just add a drop of cal mag first so that you can get it to the range you want.
In regards to spring water I'm not massively clued up on it, although I would be careful because I know of someone that used it and killed their plants because there was too much natural calcium in the water... That being said, that is the one and only account of spring water being used that I know of, I'm sure there are endless amounts of people the use spring water to great effect. I guess it's just down to what minerals are in the water in your area and the amount. Be sure to check your PPM before adding nutrients, so that you can gauge how much antes is safe to add at the different stages of your girls life.
As far as I know, Bubbling your feed won't change your pH. If I was you I'd do what you said and add some airstones to your water. Oxygenating your feed can only help, I guess!
One thing I will say is, every time you add some nutrients to your water, stir it well, each and every time. Then let it sit for 6 about hours before you pH, this gives everything time to settle and will give you a truer reading!