If you activate the ability multiple times during the same turn, Vectis Silencers will gain multiple instances of deathtouch; however, multiple instances of deathtouch are redundant. A creature dealt damage by a source with deathtouch is destroyed as a state-based action the next time they are checked, so a single regeneration effect will save it regardless of how many instances of deathtouch the source had at the time damage was dealt.