If fearful , try it on a plant that’s double or only just (1) and watch the results for a few days and see what happens and also after you apply it in the Rez if you have a ph probe, look at what the reaction is. Also a big tip for all liquid based stuff ( exp salt based ) shake the fucking crap out of the out bottle ( I’m talking 30 seconds - 1min,too many people play pussy and only do it like girl or a few seconds and think that’s going to work, exp for old stuff) problem is so many times when I shook my stuff man I can feel stuff on the bottom finally “re-brewering “ per day meaning it would conbine and if I wouldn’t of been so ocd , you would be just applying god knows Math % or just water ? this is also why I use mainly dry amendments indoors for cost reasons and logic and also I think having tons of bottles of just water is just silly ( not gone a judge ya or give ya advice on that but that note )
‘my guess that stuff you have will last Inless it becomes salt , and you could read water again. Because it was a dry amendment before that and they x10 ya and it won’t ever spoil On ya . But like all nutes I wouldn’t waste it ( if it was me ). And if 3rd option you could check the products label and see what’s in it and see if it has a super limit shelf life? haven’t seen many products non organics that aren’t and it’s mainly non logical regulation on shelf life vs what should be used on alot of ferts or even bennies/fungi ( so if you know what’s in it, that’s the key )