Old bottles of Seachem Prime still usable for reef tanks?

[Jonathan lee]

I ordered a bottle of Prime from a pretty big lfs/pet store and when I received the package i found 2 bottles in smaller size to make up for the 1 bottle i ordered. Either they ran out of the size I ordered or they gave me two smaller bottles cause they wanted to get rid of the older stock. Ok so the bottles have yellowed abit. Which is what ive seen at a few Lfs over here when the bottles stay on the shelf too long and exposed to the light in the shop. Since Prime will last forever if kept at room temp and dry, im assuming these 2 bottles still can be used although based on the serial/prod number i see on the bottle and the old review from a customer in 2021, they were prob made in 2020. How do i test if it still works as intended without a chlorine test kit? Has anyone used seachem products which bottles have turned abit yellow?

 

[Reeferbadness]

following. I have a bottle from 2021 sitting in my fridge and am not sure about using it also