Kosta's answer basically covers it. An essence is not a source. The source and point of unity in the Trinity is a Person -- the Father, not an impersonal and abstract "essence" or "God in general." The Father, Son, and Spirit are of one essence, and that one essence is uniquely enhypostasized in its entirety in each of the persons -- it is not divided up between the persons.
Thank you for the both of your explanations. I didn't mean to infer that an essence was a source! Again, we are probably speaking apples and oranges. As you both have said in the past, we cannot comprehend the Divine Essence, so what occurs "within" the Godhead is really speculation. I am quite aware that the essence of God is not divided between His persons!
Regards