I totally get it. Every year I get potting mix from the same commercial soil blending business. They blend it to your specifications. I get 60% perlite, 20% finished compost, and 20% coconut fiber. Time release fertilizer is added during mixing. It comes in 4' x 4' x 4' bags. This year, for the first time, the perlite has been turning brown after it's been watered a few times. I suspect they used raw coconut fibers. Next time I'll specify washed fiber.
