I'm sure that it has just been exposed to light which usually changes most whitish rc's into a yellow tint, and would continue to do so especially if that capsule is't closed tight and is continuously exposed to air. And the clumbiness is usually caused by moisture. I used to keep my a-pvp sometimes in a little plastic container in my pocket and if I'm was working and would get even just a little bit sweaty or if it was a pretty humid day, the powder would quickly clump up. Mostly turnintg into little mini pea sized balls.
Just IMO, I doubt this has heightened the toxicity of the chemical, and more than likely has lost potency. All chemicals have a self life. It depends on how you store them on how long that shelf life is. I try to keep most of mine in a dark, dry, room tempertured place, where they are atleast double bagged and inside an air tight glass or plastic container. I'm sure there are better ways but that has seemed to work for me and does the job without much contamination or discolor of the chemical.
