I personally don't ever stop with the calmag.
I do however reduce the
EC of my nute solution towards the end. The plants just don't use/need as much as they would in peak flower
When using floranova in any medium EXCEPT coco, I never, ever needed to exceed 5ml/gal of the floranova. I will usually drop it down to say 4ml/gal, when i'm 2 weeks out, then MAYBE 3ml/gal for the last week.
If in coco, I'm usually doing 4ml/gal of floranova bloom, and usually 2.5ml/gal of calmag(this amount depends on the hardness, or lack of, in the water i'm starting with). I would usually reduce each of the floranova AND calmag down around 25% for the last two weeks.
You could reduce even further if you really wanted to, but I USALLY only reduce the nute strength by about 25%.
It really depends on what your plants look like though. Sometimes i'll reduce 50% for the last week
Like I mentioned in another thread, check your run-off. It will show you that they start using less, towards the end.