About half of us would say we never just periodically worm our chickens unless we had a reason or sign. The other half would say they do it regularly, like every six months or so. Your choice there. Safeguard is the one I'd turn to due to seeing that being popular here, but we've never wormed our chickens in 8 years, albeit using Ivermectin for SLM.
As for scaley leg mites, we've had them three times. We have silkies who are prone to those. The first two times we slathered their legs in vaseline every two or three nights for a total of three times.
The third time we had double the chickens so I didn't feel like slathering 30 some legs and feet. We applied two drops of Ivermectin Pour On 5% on the backs of their necks and repeated that in 10 days. Ivermectin is considered a dewormer too, so you could kill two birds with one stone!
Bad feather quality can be improved usually with higher protein. I'd try putting them on an All Flock 20% and give them oyster shell in a container on the side as all flock is low in calcium.
The one with lesions on her face and vent, maybe you could post pictures of that. Could be a pecking issue or something else?
