You really need to be precise here. Everytime I had problems in my Coco grow it was caused because of pH. I finaly bought the blue lab pH meter and its working amazing I use CANNA Coco and ph 5,8 is ideal for the plants in this type of Coco. Only 5,8. Not 5,5 or 6,0. 5,8 really works best for me.
About the First seedling feeding @Undead-Toker. Its really surprising for me that you dont feed them at all for the First two weeks. I tried this and it didnt work for me at all So I started to feed them right away since I put the germinated seeds in the Coco. I use all of the advanced nutrients products and my EC is 0,8 pH 5,8. And they seem to love it.
Rinsing Coco? Just dump some of it in to tak water and measure the pH and EC it will tell you more. I lower my pH to 5,8 in 1 liter of water and then I dump a Hand full of Coco in to it and check it. CANNA Coco has EC about 0,04 and pH is stable at 5,8.
Edit: how do you take those macro pictures?