Do you use a serum or protective spray?
How old are your irons?
Are they losing any coating?
Be careful with straighteners some on the market today get VERY hot and everyday use will damage your hair, however if you leave a protective spray on your hair or serum this will minimise damage. Also try and avoid snagging your hair with your irons when hair gets very hot and if its colour/bleach treated it gets brittle, tugs that your hair could normally withstand can be alot more damaging in this case.
If your irons are losing any coating on the plates its time to change.
In a nutshell look after your hair with protective sprays intended for use with straighteners and try and use your straighteners every other day. Flyaways are normal but excessive breakage is a warning sign to ease up.
Hope that helps
xx