The coco dropped the pH to 6.0, and raised the ppm to 1580 (salt?).
[attachment=o219676]
[attachment=o219677]

The peat dropped the pH to 5.7, and raised ppm to 1490.
[attachment=o219678]
[attachment=o219679]

This was like a slow, "deep watering" over 10 minutes or so. I'd expect a straight-through, flooding flush would give less deviation, and that holding the water for awhile (as a plant would) might give wider spread results.