Just before 10 minutes ,I have received pre-arrival letter by mail.Moreover,I have received 2 medical forms one for myself and other for my wife.These both mail received separately and automated generated and do not reply.Did you receive direct email or through MyCIC account?
It is not mentioned to do re medical but written as find attached document in mail.
I think within 10-15 days good news may come.I have already written that our medical is still valid up to 07-2-18 and already in Canada as visitor visa and can send passport.