I think you have enough fire power to light the stage the question is about position.
Footer gave you a good strategy but in order to really help we need to know the degree of beams on those S4 jr.s, what
lens is in your S4 Pars, and what beam spread lamps you are using in the 64's. Also we need to know your "Throw Distances"? To calculate your throw distance you have to go back to your high school geometry A squared +B squared= C squared. A typical calculation of throw distance is:
(Height of the
instrument above the level of the stage - 6 feet) squared + (Horizontal distance from the instrument to the target area on stage) squared= (throw distance) squared
We remove 6 feet because we are concerned about the distance to head height not the floor.
Finally you mention 3 electrics on stage but nothing about lighting from out front. Do you have any? If you have no lighting positions out front anything we say won't matter, the faces are always going to be dark. Ideally, Proper front light consists of 3 lights all at a downward angle of about 45 degrees. There should be one pointing directly at the person from straight ahead and one coming in at a 45 degree angle from the left and one from the right. All of these should be out over the audience. For positions farther
up stage you may be able to use your on stage electrics to get these angles.
If it isn't 45 high, the person on stage will have more difficulty being blinded by the light. As you move the light above 45 high then you will gradually get more downward shadows on the face. The two 45s to the sides eliminate side shadows on the face and to make it evenly lit from ear to ear. Sidelight, backlight, and down light from on stage all help to fill out the full dimension of the person, but without at least that one properly positioned front light you will always have dark eyes and faces.
(Charc all good points. I just think the problem is poor front light.)