pH of RO or distilled water means NOTHING. Ignore it. Only pay attention to the pH of a solution that has a stronger ionic strength.
Your plants look great.
a TEASPOON of Epsom salts in a gallon? Yikes. That is NOT good. Next time you water, do a HEAVY watering with plain water and then give a complete grow fert at half strenght. Why did you add epsom salts? There's NO Mg deficiency on your plants.