That would be near impossible and it happened to them the exact same day as myself. It's quite odd how everyone claims its a dance when other websites not within my control had gotten affected as well.Have you tried contacting the other person that had their rankings tank as well and see what they did/didn't do to trigger their drop? Might be useful.
Yes Negative is possible and can damage all your sites. I have full information about that
Have you blocked backlink crawlers ? If not, you need to do that to be under radar of your competitors prying eyes.
Also, domain registrars don't make much of a difference if you have just 10 domains.