I know this forum is for IVV not IHVV but it doesn't seem like...

I know this forum is for IVV not IHVV but it doesn't seem like there's a forum for IHVV... Anyway, my question is, why on earth has IHVV dropped 18% today?!? IVV has barely moved, as has the AUD. The S&P 500 barely moved as well. I can find no logical reason for this huge move. I just bought $30,000 of ihvv, in case this is some beautiful glitch (if it's not I'll sell, nbd). Is it some time sort of weird 20% stock split or something? What the hell is going on?