Question about coco coir?

I am running coco coir and was wondering if this is a problem or normal. I am watering with a 5.7 ph solutions ppm to 600 or so and I water to a good a good amount of waste example 1 gal to 2 gallon smart pot 2 1/2 - 3 gal to 5 gal smart pot every 2 days. The runoff ph for the 3 are 6.1-6.2 and the ppms are around 650 in the 2 gal and 750 in the 5 gal does that mean that the ph is off and is it minor salt build if any with the ppm being just 50-100 ppm more than the beginning solution just wondering cause im trying to get them up to about 800 or so ppm there week 5 flower.

your numbers are actually fairly good. I see no large problem yet but you do have minor buildup. watch for your runoff ph to start dropping too as the ppm rises. it's another indicator.
salt build up can be corrected with more runoff

Before I switched to the pH perfect, I was keeping my nutes between 6-6.5 for my coco. If you're really that concerned about any salt buildup, just skip the nutes a cpl feedings. Gluck