As I look at the diagram again, I'm guessing you lost only 1/4" on each of the A and B legs of your triangles if you used a 1/4" seam allowance. Doing the math again with that in mind:
Legs A and B are now 4.625" long. 4.625" x4.625" = 21.390625 sq. "
21.390625 sq. " + 21.390625 sq. " = 42.78125 sq. "
Square root of 42.78125 sq. " = 6.5407377" which is within spitting (and quilting) distance of 6 1/2 "
If I were you, I'd square them to 6 1/2" (unless some are too small - in which case I'd square them all to match the smallest one :-)