Good GH Flora Series Ratio For Mag Def!

I have a magnesium def on my ladies and cant get any CalMag for another week and a half so im wondering if anyone knows any good ratio for the GH Flora Series which would be a good temporary hold until I can get the CalMag?
My ladies are about 6" tall and they are growing in peat/perlite under 600w MH!
Anyone know how I can supplement this for a week or 2? Im following the GH Flora feeding schedule at 2/3 strength...

try some epsom salt at about 1 tablespoon per 1gal of nutes