Mixed and stocked dry fertz

Greetings,

Was wondering if anybody could help me with a small problem. I had previously stocked a mix of K2SO4 (50g) and MnSo4 (0.18g) in a small container for future dillution into a 500ml distilled water solution. It was stored in a dark place maybe for more than 4mos. and when I took it out I noticed the dry powder mix had turned into a brown color which was previously white. Is this still usable? I'm a little weary of using it now since it might have turned into something that is utterly useless for the plants as far as nutrient supply or worse it might already be toxic to the fauna. Need your help guys.

 

Thanks for the reply Snoozer. But I can't add HCL nor malachite green since it's still in dry powder form and was just about to add it in DI water that's when I noticed that the powder had turned color from white to brown. I think it's a chemical reaction between the 2 powders (K2S04 & MnSO4) since I have about 2 more small containers with the same dry mix and all of them had changed color.
Well I really just wanted to hear from someone who knows more about this.

 

Thanks VaughnH! I think i'll try that mix in my uglier planted tank.
On the question regarding MnSO4... It's included in my DIY GH booster mix.
Thanks again!