I just did some research, and I realize that OTC companies CAN dilute stock without filing with the SEC, and that this could be what happened.
They would have to increase their Shares Outstanding figures and their Float - but they can do this...and in fact, there are many company scams that do this intentionally just to take investors money.
While I DO NOT think that ZVTK is a scam (it clearly has a successful product, and it would be foolish to risk that on a "scam"), it is quite possible that dilution was the cause - or at least part of the cause.
I stand correcting myself - although I still think it is unclear it is possible it may have been diluton, or a combination of dilution and manipulation by MMs.
"The difference between a successful person and others is not a
lack of strength, not a lack of knowledge, but rather a lack of
will." --- Vince Lombardi