Since they are mostly bias seams, try what one quilter above suggested.
Take each diamond to the ironing board, and place on a drawn diamond that is
the right size. Spray with starch to moisten. I use Mary Ellen's Best Press
since it leaves no residue. Pull the defective diamond until you approximate
the correct size and press.
I apologize if you have already done this ad nauseum.
If it didn't work then you should do what gal288 suggested with the sashing
and outlining suggestion.
Best of luck.
I found Jan Krentz's book on Lone Star Qlts from C&T publishing to be
very helpful.I at first thought it was wildly obsessive-compulsive, but it
works. She also has patterns that have diamonds around the outer edges
of the central Lonestar so if all else fails you could redo some of the
Lonestar diamonds over and use the misfits for the outer area.
I don't know how to upload pictures but your library might be able to get you the book. If you Google Jan Krentz Lone Star Quilts and beyond, the cover quilt shows a star with 8 edge diamonds. Her site charges $25 for the book.
Amazon has a used copy for $12.79 - Judy