I think your injecting them with fluid that is not strong enough
get a small wax cup and add maybe 1/4 cup of water. then add your normal 1tsp of kalk
. Mix it up as soon as you add it. then take your syringe (you really dont need the needel) and pull up 1 syringe full. then get close but not touching it. and give it a good slow but steady squirt.
will precip as soon as it hits the water but thats ok. This should kill it and kill it good.
I use a syringe I got with some 'target invert food'.