Confusing problem "pics inside" Help!

Hey guys to start off ill give you details of the setup and so on then talk about the problem and stuff ive used to help so far.

Im using a 600w cfl light, with miricol grow and have been using rain water out of my waterbutt outside.

The strain is trainwreck and has grown fine until 1 week ago it has these od spots on the leafs, looking threw the help pages it looks like magnesium/calcium deficiancy so i baught some sensi cal / mg mix bloom, i used it yesterday and today there is no signs of it stopping.

My question is how many times should i use the sensi mix and is this actually a deficiancy.

add it in every feed. give her a foliar feed too if u want. the spots wont go away but new growth should be unnafected.

also check to make sure your ph is right as that could be causing your problem and giving extra cal mag could just make things worse