I know a sparrow isn't quite the same as a chicken.. but I just had a sparrow with wryneck and I gave it two drops from a 200UI softgel twice a day (first feeding and last feeding), and two drops was at least half the softgel or 100UI. I also gave a dusting of selenium (it aids the absorption of vitamin E) and I gave a scrape of a B complex mixed with a drop of poly-vi-sol mid day.
minor results took 36-48 hours, but then he started getting better quick.
I wonder if, since this sparrow was half an ounce, if the dose of vitamins could be increased for these larger silkies?
Vitamin B is water soluble so you can't really overdose on that. Vitamin E does have side effects if doses are too high, but if they are so deficient it is affecting them neurologically then maybe larger doses are called for for a few days. At least this is my thinking. As far as I could find there aren't any long lasting side effects from large doses of vitamin E, the body recovers from it very quickly if it is given to the degree of causing side effects like tiredness, weakness, nausea etc.
Good luck, I hope your babies recover soon!