All things degrade. Like food, nutrients have expiration dates so you can be sure the product is as advertised.

Unlike food, you cant tell just by looking at it or smelling it.. so relying on the expiration date is probably the safe way to go. That being said it's not like 1 day past the expiration date is going to make a difference.

If they are too old, you will find strange hard to diagnose deficiencies and lockouts. It's up to you if it's worth finding out or not. Personally I wouldn't use anything expired. But my stuff doesnt sit around that long, so I've never had to make that choice.

I will tell you, I had a friend who had massive nutrient issues. For weeks he was trying to figure out why things were going wrong. I checked the dates on his nutes and they were over a year expired.

He bought new nutrients and the problems were solved.. nutrients arent expensive, specially when you're like me and dont use 1 million un needed bottles of stuff.