Judging by how bright red their combs/wattles are at this young age, I'm guessing they're roosters. But their body shapes are still so hen-ish I wouldn't bet the whole farm yet. Sometimes there will be an early-maturing hen whose comb/wattles turn red this soon.
Over the next few weeks you should be able to tell for sure. You may soon hear some thin & rusty crows coming from them early some morning. You can also part the feathers on their necks (hackles) and on their backs just in front of their tails (saddles) to look for pointy boy-feathers beginning to grow in. Look at pictures of full-grown roosters, notice the fringes of long thin feathers on their necks & saddles, only the males have these. If you see them starting to grow on your chicks, you know you've got roos.
Did I read it right, did you lose your last pullet chick? If so, I'm so sorry. Why don't you post a question about that, describe the symptoms, post some pictures of your coop & pen. Maybe we can put our collective heads together & help you figure out what happened.