There have been no changes to the formula in a couple years.
There ares everal possible explanations.
There are two versions of Zone Perfect. Both include a yellow and a red dye. The red dye is lighter and can come to the top if the product settles for a while. This will give the Zone PErfect a pink look when viewed through the opening in the top of the bottle. Shaking it up should correct this.
Yellow dye can also go bad with age. This may have happend with product that sat for a while or could have happened with dye that became unstable in our facility. With the yellow not rpesent, the product may look more red / pink than usual. This would not effect the cleaning performance.
When mixing taks get changed over form making one product to the next, they should be rinsed with distilled water adn blown out with air. Sometimes that does not happen as wellas it should. Then a residue of product A may get mixed in with the first few gallons of product Z changing the color and/or slightly altering the pH which can affect pH sensitive dyes.
None of these should affect the performance of the product. But you will be able to take it back to distributor for a credit if it does not work as it should or if you are concerned about it.