Fertilizer Expiration?

[MT-Phal]

Hey all,

Does fertilizer expire? I bought some MSU RO, the hard grainy kind that dissolves in water, two years ago. I've noticed that over time it started to harden and lose it's color. It was originally very sky blue, now is lighter and there's some browning within the bag. I've also noticed that once mixed the solution is clear where it was once light blue.

The bag has always stayed sealed when not in use and squeezed to remove any excess air, while stored in a cool and dry cabinet. Still safe to use or should I chuck it?

Thanks.