My cousin asked me to take her three hens for the winter (that's actually code for 'please take my hens forever') she moved way up north and was worried about bears and lynx killing them (of course I knew they would stay once they got integrated with my gals).I've used verm-x last year in my flock. It's meant as a natural preventive but it doesn't claim to kill worms in case a hen does get them. I didn't have a fecal float so I can't be sure, but I supposed at the time that two of my hens who were very unwell months apart, Vanille and Caramel, had worm overload due to their symptoms. I treated them with Flubendazole. In both cases they healed when I thought they would pass, but it may have been a coincidence. So from my experience I'm not saying that verm-x is completely ineffective, but I'm not sure it would be sufficient for a chicken that is already fragile if there are worms in their environment. The other problem with it is that it has a very strong taste and smell and clearly the first of my hen to be ill, Vanille, didn't drink much of it as she hated it.
Sorry for the long post. I also agree if Flexi accepts to eat normal pellets, eventually made into a mash, it is better to give her that. If she hasn't been eating for more than four or five days I would understand giving her confort food.
About a month after they arrived Sophia became very ill, I was freaking out thinking I was somehow killing her beloved hen. I had my vet check for coccidiosis and worms, nothing.
The only thing was that she was going through a heavy molt, the vet suggested she was stressed from the move and the molt.
She wouldn't eat but drank lots of water making her stools pure water. In desperation someone here on BYC (that's how I first met everyone here

She finally turned around and slowly started eating again, but it took about 6 weeks for her to get back to normal, and get her splendid feathers back.
Of course this happened in the Fall when it cold at night so I would put the radiant heater for her, when she hardly had feathers.
Now I am more wiser and experienced - next time I will start the scrambled eggs and supportive care sooner...
Who knew chickens would be so stressful!!