I'm curious if anyone else has suspected/experienced this... I buy this product from Walmart & Lowe's and always make sure the mfg date is recent, but even so, I've noticed that some product is more yellow in color than other, I've also noticed that sometimes a gallon doesn't increase the FC in my pool like it should, sometimes by 50% (I add the gallon, wait 1-2 hours while the pump runs, then test). I'm suspecting that the less yellow product maybe has been stored in the heat and/or sun and has lost much of its sodium hypochlorite - does anyone know if this is possible given they come in white (but plastic) bottles? Can heat affect these bottles or only direct sun? I wish I had an easy way to test the concentration of one of my bottles, but looking online it looks to be not so simple. Any thoughts would be great, thank you!