Nutes shelf life. How old is too old?

I have been having a problem with my girls. The new growth near the light is coming in very yellow. After trying to diagnose the problem it looks like Zinc Def. I have a aircooled hood with A 600w HPS. WW in first week of flower in a drip system. Iam wondering if the flora nova grow I am using might be too old. It has to be about 3 years old. Just started developing this problem first one plant then another. The room stays in the mid 70's. Humidity has been low and now is up to par. One other thing the growth is abundant making me think of trimming some leaves. I will be swithing over to flora nova bloom. I am going to buy a new bottle of that. Any help will be greatly appreciated

My nutes dont stay around long enough to go bad, but I would say that after 3 years the quality might have diminished. I would try a new batch and see how differently they react.