Yep, had the same thing happen to me in one of two bottles of MesoSilver that I had stored in my closet for three years & forgotten about. It happened last summer.
I used the first bottle no problem, got halfway through the 2nd & fuzzy stuff started appearing at the bottom of the bottle. By this time I was already making my own CS & had never seen this before. Needless to say I pitched it, but something got into that bottle that liked growing in the CS.
I was using the Meso topically & for gargling. What I think happened was that I introduced microscopically small skin particles into the CS & the nanoparticles of silver began attaching to those skin particles setting up a cascading agglomeration of both silver ions & nanoparticles.
What I had been doing is dipping the same finger through the top of the bottle that I used to vigorously spread the CS into my skin in the area I was treating for a fungal condition. Of course everytime I dipped my finger back into the bottle I was introducing skin cells into the bottle containing the CS thus introducing non CS particles causing agglomeration.
I've stopped doing this & have never seen it again. Another thing, do not drink directly from your CS storage container, pour it into a separate glass first. Drinking directly from your storage container will probably introduce very tiny saliva droplets into the CS as it backwashes from your lips returning to the bottle. Don't forget, your mouth is filled with small skin cell particles.