Help My Chickens have WORMS!!

[D SCHWARTZ 26]

I sent a Fecal sample to my Vet and they found Roundworm and Strongylid eggs. She said to treat them with piperazine for the round worms and that the strongylid shouldn't effect them.
My only concern is that I treated my old laying birds for round worm in the winter and thought I had gotten rid of them, so I got new ready-to-lay hens early spring; now this fall already I find out we have WORMS AGAIN. (Im so discouraged) My questions are: Why is this happening and how can I make sure that I get rid of the worms and keep them away? And should I be treating for these strongylid worms as well? And is piperzine the best treatment?
Thanks!!

 

[D SCHWARTZ 26]

I forgot to mention that the reason I sent in the fecal sample to begin with is because my chickens had almost stopped laying and a few of them were getting really dumpy looking. They had ruffled feathers, stiffness when the walked, tail would hang low and they would just stand there mostly with their head under their wing in the middle of the day. I've also lost a few younger chicks as well. So I thought it was coccidiosis that's why we got the test but it came back clear of Cossi but they found these worm eggs.
So I'm really at a loss now of what to do.
Any help or ideas is appreciated.