This time of year free ranging birds can get rangy looking, hence the term "rangy", meaning they are ranging so much in search of fall vendor that they lose excess fat at times. Mine are looking extremely rangy right now due to a drought we had at the end of summer and into Sept., which reduced the amount of feed they usually find out there in the fall....often they come into winter fat as ticks on just foraged feeds and only a little grain based daily rations.
I wouldn't increase proteins or any other such things that most people advise, as I've found it actually will have the opposite affect than desired. My birds will look thinner when given more protein, so I actually bring the protein levels down towards winter by mixing some oats and a little BOSS into their 16% layer mash. They need a lot of crude fiber in the winter months and oats are good for that.
I don't deworm....used to give garlic now and again but I don't even do that any longer. I've been butchering birds so long now, checking intestines for signs of parasites each time and never finding any that I see no point in it.
If I had a confined flock I may do it, but with free ranging birds I've found they will often find their own deworming agents....one of the most prevalent I've found in their crops and gizzards is what we've always called "saw grass". It's the same type of grass that carnivores will chew on when they need to rid themselves of parasites...I've seen my dogs and also my cats chewing on it. These are tough grasses that have little nutritional value, very high in cellulose, so no real reason for chickens to consume them other than the deworming factor. If you run your finger down one of these blades of grass, it will cut you...and deeply if you aren't careful. Works much the same as folks claim DE works.
Messy butts are not a sign of worms, no matter what some YT channels will tell you. If your birds are 6 mo. old, it's likely they are at POL, which loosens the ol' pucker string quite a bit and they can't pinch off a loaf as well as they can when not laying actively. My granny always said the hens with the messiest butts were the best layers and I would have to agree with that...those are the daily layers of large eggs. The cloaca(vent) will loosen, swell a little, moisten and gape when a hen is in an active, daily laying cycle...this can all lead to poop on the feathers below the vent.
A hen not in active laying cycle or only laying sporadically will not have as loose a vent and usually won't have a messy butt at all. They have a tighter, dryer cloaca.
Most of my 5 mo. old pullets look rangy right now too....you can actually SEE the breastbones on them, no need to even feel of them. I don't ever worry about that....soon that breast will smooth out, look plump and womanly, and they will be ready for mating and laying.
Just give them time....
to the slimy offerings to be had in the cans that line the shelves at the grocer!!! 
