my son and daughter are teaching each other purging methods as well as starving?

[Marylin B]

Today when i came home from work i heard my 14 year old daughter and my 17 year old son teaching eachother methods on how to purge after they eat and how to starve themselfs without me knowing . i was in shock i new something like this was going on with my son but not my daughter and let me tell u she has some good methods from what i heard . i didnt even know they say more then hi or hey to each other much less this . how do i confront them since i didnt at that minute since i need to think this through. i want to tell them seperatly about there eating disorders and not have my 7 year old know . how do i occomplish this and what are my treatment pptions for them?