The watermark is because their pictures were/are being stolen and used in other hatchery/scam sites.
Also to combat a.i leaches.
Chickens aren't always cooperative when picture taking.
They sell it at a feed store or garden supply, look for Garden Dust.
Just dust or spray them, dust is easier, you can pour it in a sock and Bop them.
D.e will not help mites and will complicate breathing for you and them.
They happen, it's OK.
Get some permethrine based spray or powder, clean hour coop out completely, burn the litter, treat the coop and the birds and get all new bedding and litter.
A brief look at a few pages and I see misspelled words, lots of misinformation, no sources listed, no photos of their own birds, bad photos and impossible stock.
It's likely a scam.