Woke Up To Find A Small Group Of Tetras Left

[This Old Spouse]

I've been hearing about people having problems with plants that come from China, because they use all sorts of chemicals and such. It seems too coincidental the fish would start dying when you introduced the plants.
 
Hope you get it sorted out. Sorry for your losses; that can be so devastating.

 

[Shelster]

I always give all my new plants a good rinse under the tap before planting in my aquarium.

What a pain! Have you removed the new plants? Your tank looks great in your signature, how annoying!!

 

[mark4785]

I will second what has been said above; be sure to clean your plants before introducing them into the aquarium. I place my new plants in a bucket filled with mixed hot/cold water (from the bathroom faucet) containing either a weak bleach (Interpet pond disinfectant) or an over-dose of Sterazin. 
 
From experience though, any traces of ammonia in a tropical aquarium can take your stock out pretty quickly so it could be that your ammonia level was to blame here.