Hmmm...well, two things spring to mind as possibilities--

Because Silkies have heavy foot feathers, they can be susceptible to mites. Check the birds' legs for scaley mites. If the scales of the feet and legs look rough and/or lifted, they have scaley mites. They are a tiny mite that burrows under the scales.

You can treat for scaley mites in a variety of ways, either spray their feet thoroughly with a lice/mite spray (in my experience the best way), dust them or use oil. I use Adam Flea & Tick Mist with IGR (Insect Growth Regulator--make sure you get the one WITH the IGR, the protection lasts for three months!), spraying all over the bird except for the eyes, and working the liquid down into their feathers. Sevin, made by Ortho, is an insecticide powder that can be used on chickens, but since it's a powder it can't be worked into the scales of the feet well enough to do a thorough job. You can also just plain smother the mites using olive oil or Vaseline--just gloop it on and REALLY rub it in. I don't suggest the oil or Vaseline for silkies though, as it really gunks up their feathers. If you suspect mites, you need to treat ALL your birds and their entire living quarters, otherwise it's like showering and putting dirty clothes back on--you havent really solved the problem. Once a bird has had scaley leg mites and the leg scales are lifted, they never go back down, even if the problem is cured. We've learned from experience that we have to worm (for internal parasites) and spray (for external parasites) our birds and their living quarters twice a year, like clockwork.

Another possibility is a condition called Bumblefoot, which causes large, painful lumps to appear on the underside of the foot, in the pad areas. If you search Google for 'bumblefoot in birds/chickens/poultry you'll see some icky examples. These lumps can turn into open sores which hold dirt and bacteria very nicely, thank you, and be Hellish to clean out and KEEP clean long enough for the area to heal (which goes slowly). You'd have to clean out the wound very well, then put the chicken in an enclosure with no dirt on the floor--and wire bottomed cages can aggravate the condition, as can the bird walking around and stepping in it's own feces. Fun times. Bumblefoot is usually a lifelong problem for affected birds because of the 'impossible to keep it clean' issue.

You need to grab your silks and inspect them closely to see what's up. More info on my chicken site, here:

http://home.earthlink.net/~velvetsparrow/VSChick.htm

...and on my friends' silkie site (he is a breeder/silkie shower and knows his stuff!) here, read the 'articles' section:

http://www.browneggblueegg.com/index.html

Velvet ~:>