I understand you were trying to be helpful. In my 25 yrs of fish keeping I have never heard that Planarian eat snails, I still didn't see that in the links provided.
It was not my intention to be sarcastic I'm sorry you perceived my post that way. If my post had been just for you I would have...
Using chemicals of any kind in your tanks should be a last resort. Even though the package may say it won't hurt your fish or plants many times it will weaken them and this leaves plants and fish open for disease.
If you are having a Planarian or snail outbreak you are most likely over...
Since they've been stressed to the max you might want to keep their water about 82-84f and do extra water changes to prevent Ich and other stress related diseases.
So glad things turned out well.
No not really. Snail over population usually indicates overfeeding of the tank.
A good vacuuming, a large water change, reduction in feeding and manual removal of excess snails should go a long way toward controlling them. Finding why their over populating is the only way to control them.
Sorry to hear you're having problems. Are they going to reship? Or the post send the package on to you. You will need it if their dead to take pics as proof. In extreme cases they could still be alive.