You cannot kill them this small using only tap water so if i were you i'd go ahead and flush those baby's out with Ph adjusted water- no nutes - just to be on the safe side. and they'll be just fine i'm sure
start feeding VERY carefully when the new growth looks healthy and growth picks up.
Tap water has nutes and micronutes in it. My water has an EC of 200ppm ( ec* 500)
Good luck with it mate.
Just let it sit for a few hours for any chlorine the water company may have added to evaporise. Or call your water company and ask if theres chlorine in your tap water