Waaaaay too young. Its sometimes hard to tell for almost adult silkies. Let alone babies. My silkie chick is 6-7 weeks old and im not even close to being able to tell
Too young Silkies are slower developing, so please post pics of the whole body, crest, and comb with crest pulled back at 12 weeks. Of course, if ou see any comb growth or redness, ou can post earlier.
My silkie hen did not start laying until she was 11 months old. I heard that it can take up to 6 months to sex them but that is rare. Usually you can tell if it is a rooster when they are 3 months old.