Yeah I done a bit of that as well added some water, and I also added some nutrafin cycle stuff for a few days, I know that that stuff doesn't cycle the tank, but I figured adding water the cycle stuff and filter media from my 3 year old tank would be ok, obviously not.
It was very bizarre one night they were ok the next two were dead, then later that day another died, so I then thought to add all of the other fishes (7 more) to the tank with the filter and within 10 minutes of getting the filter another had died even though it was swimming a second ago, and now all the silver tips are gone but the other 7 remaining are fine, now I'm nervous about taking out the filter it's been there for about 5 days.