Ask-a-Dave's-Gardener: Window box herb garden help, 4 by TwinkleTits

TwinkleTits wrote:
So I am a beginner gardener.. I really mean it when I say it. I just went to the store and didn\'t realize there was a difference in potting and garden soil. Needless to say, I bought the big bag of garden soil to plant my new herbs I bought into the window boxes I also purchased. I then realized the bag said \"not for containers\" and to mix with the ground before planting when I went to set it all up. I then read you can make potting soil from an equal mix of perlite, peat moss and the garden soil. I got perlite and shagnum moss and attempted a mix that I don\'t think I did too well with. The soil has been wet for days and my kale seems to have formed white spot from what I looked up online. I know I have to get rid of it and start fresh. Should I worry that my other box will have the same issue? Also advice on good soil to grow my herbs in the pots and any other helpful tips would be greatly appreciated. I will hopefully be able to figure out how to post pictures so you can see what I\'m working with.
Thanks guys!
Soil- miracle grow vegetable and herb garden soil
Perlite- miracle grow (enriched with plant food)
Shagnum moss- pictured below (or wherever it ends up in the post. Lol)
I am in northern east coast Florida with an east/southeast facing balcony)