I see, then likely it's damage from mating.
You can try a saddle, but those don't completely protect a hen from feather damage.
I agree with checking the nails and spurs.
Is she eating/drinking o.k. - no signs of hiding or running from the roosters?
Separation can also work. I'm not talking about getting rid of birds, I'm talking about penning up 1 or both roosters - give them separate quarters or pen them occasionally to give the hen a break. A lot depends on your set-up.
Getting more hens may help, but how old are they? Are they mature, started pullets, etc.? How do you plan on quarantining them and then integrating them? How much room do you have - coop/run space. Do you have a plan if things are not going well and need to make some separations?
These are things to think about. If you do not free range and confine your flock like most of us do, you need to have some measures in place for separation. Nothing may happen and all is well, but being prepared goes a long way.