Welcome Angel,
Like Mainiac said, "The longer the arrow the more flex. Shortening an arrow stiffens it."
These, too, will stiffen a weak arrow:
-reduce point or insert/adapter weight
-add weight to the nock end of the arrow (more or heavier fletching, nock weights, wraps, etc.)
-add more weight (strands, silencers, serving, nock points, etc.) to your string
-raise brace height
-move a plunger or riser side-plate thickness toward the arrow on the rest (by adding thicker leather, velcro, double-sided tape, etc.)
There are others that will stiffen, but also you can reverse these to weaken an arrow no matter what shaft material you shoot.
Just get her tuned, and shoot straight.