Overpowering stench coming from small flock

Frist, I’m new to raising chickens so I apologize if this post sounds a little silly. A couple of days ago the owner of the gym that I frequent approached me and asked if I could watch over his friends flock (7 hens and 1 bantam rooster). I have a decent size coop, which could handle another 50 birds without issue, so I told him I’d look after his flock. I told another friend what I was going to do and he told me I was crazy to bring any chickens into my coop. So, thankfully I did some quick reading and decided against bringing them into my main coop. Since I committed to taking care of this man’s flock I built a 16’x16’ coop to house the birds. While I was completing the coop an elderly man arrived with his birds, so I placed them in my trailer to keep them safe until I finished this new coop. Now, to the issue: Those birds have a stench! I have 38 chickens in my coop and have never had a stench come off my birds like what came out of that trailer. I removed the birds from the trailer (2 hours enclosed); the following morning I returned, and they still stink!! This flock is about 1 year old; they don’t appear to have anything physically wrong with them, nor does their poo look bad. They are RIR’s probably 5-8 pounds, very skittish, don’t perch, lay eggs anywhere, and sleep in a pile. The elderly man gave me a couple of bags of lay crumble (New Mexico brand), no other type of foods. I built them a 16’x16’ coop, 24’ perch, 4’x6’ nesting box, with a dirt floor…just until I get a minute to install a wooden floor. My friend told me they may have mites, so yesterday I dusted the birds, and everything in and around both coops. The birds have fresh food, water, and some fresh fruits/veggies from the garden. I know that I treat my birds like pets and this may be common, but this smell is horrible. Thank you for any assistance. J

That's great two cents, thank you.

Like I stated at the beginning, I’ve only been raising chickens for a year, so I have a lot to learn about taking care of them. Today when I got home the chickens didn’t smell as bad, so I’m also leaning towards neglect versus an illness. They haven’t touched the nesting box or the perches and they are terrified of me. The best news is they ate a large bowl of fruit pulp, a small bucket of garden greens, crumble, scratch, and some snacks…so they like to eat. My next question is should I dust them again? I don’t want to overdue the dusting and I do it while they are sleeping to keep them from freaking out, but the last thing I want to do is harm these birds.

Thank you everyone. I’ll dust them again next weekend and give them a healthy dose of love until then.