Fishtailing isn't in and of itself a spine issue, although it is a tuning issue.
To answer the question of whether you can or cannot use them, you are going to have to tune the bow and arrow together.
Pull all the material off the sight window. Add a piece of tape as Bob Burton would instruct, and then shoo them at a vertical line. Do they hit the line, or do they hit right or left of the line? That will be your answer. If you are left handed, and the arrows impact left, then they are weak, If they impact right, they are stiff.
Weak is easy, you just add material to the sight window, until they shoot straight. Stiff not so much. You will have to add weight to bring them in line.
You can do that in a number of ways, none of which are currently "trendy". All you need to do if you don't have an assortment of field points, is to start wrapping tape around the shaft just behind the field point. When the arrows come in line, remove the tape and the field point, and weight them. That's the weigh that you need to be shooting.
