Welcome from Florida (winters) and New Hampsire. I remember being in your positon many years ago and by the way, I love the quilt you want to make.
I read that you used 5 inch Charms, which I think may have actually been 5 1/2 inches??? If they were then you need to make your small HSTs 1 2/3 inches plus the 1/2 inch seam allowance. Lot of math is needed when working this way but in the end it will be worth it.
If your Charms were 5 inches then you have another message early on for those measurements. Let us know and see what you do, please.
Good luck, Kutnso