stop testing the runoff thinking that this is an important measurement. Worrying about this is confusing you and it does NOT indicate the pH of your grow mix.
adjust the pH of your nutrient mix to 5.8, and apply it to the container of coco. Do not concern yourself as to what the run off pH is... it is NOT important to you at this time. Simply adjust the pH of the fluids going in to 5.8, and everything will be ok.
Exactly what she said! I might add.. Water to good runoff at least every 3rd day. If you can, water to runoff every day one time. Good luck!