The main point of Sapphire Gems is that they are sex linked. Males should have barring, and your chick does not. So it should be female.
I think the problem arises when other breeds are accidentally purchased or substituted for SGs. It is difficult to tell solid colored blue chicks of different...
Make sure it is getting enough to eat. I would give it some meal worms or boiled egg yolks to see if that helps. It is probably failure to thrive because the chick is much smaller than the others, even accounting for differences in breed size. That doesn't mean it can't recover, though.
If the feet are yellow then they probably are SGs. Hatcheries do sometimes make mistakes, and sometimes they just substitute different breeds. It is my impression that they have white earlobes, but I am not 100% certain. It will take several more weeks to be sure of that. Maybe 12 to 14 weeks.
Looking closer, I think those might be Andalusians instead of SGs. That could explain why the one looks raptor-ish. The pigment on the feet appears white, not yellow, and I believe these will have white earlobes. So the first blue one could be a cockerel. Time will tell.
I think they are all females. If the barred birds are definitely barred Plymouth rocks, then they have to be females because all are single barred, not double barred as males would be.
The first one actually is quite pale, but the green wash on the legs is another female trait in barred rocks...
1, 6, 7, and 9 are your definite cockerels. A few others like 4 and 8 are suspicious.
1 through 5, maybe cuckoo Marans mixes.
6 and 7 could be anything since there are many white varieties out there. They could even be red sex links crossed to black or blue chickens.
8 is a Wyandotte cross...
It has a small, pale comb, but I suspect it is a cockerel. Because of the splotchy coloring and the mahogany at the wings. Time will tell. I still don't think you could say one way or the other on this one with certainty.
He looks a lot like a buff Orpington cross, but since you say he came from a blue egg that can't be right. I really don't know of any very large and fluffy breed that lays blue eggs, so the mother must have been a mix. He is very beautiful.
He did not inherit several Legbar traits. His skin is...
It certainly looks to be a male, but Wyandotte females can get big, colorful combs early. So I wouldn't say it is 100% going to be a rooster. One thing to watch is the feathering on the shoulders. If it is nicely laced then it may be a female. If you see solid colored gold to red patches with...