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If you just got these girls this year as chicks and they've only recently started to lay, I wouldn't worry too much just yet.
What exactly are you feeding them? Do you have a container or two of oyster shell available to them for free choice feeding? Are they eating it?
When I've had newly laying pullets lay shell-less eggs, I give them a calcium "infusion". Get a large tub of plain Greek yogurt and mix some yogurt in with about 1/3 cup of the oyster shell making it thick and put little dollops of this all over their space (run or free range). Then put a few dollops on top of their feed. Do this for about a week.
You can identify the pullet laying shell-less eggs by using an old tube of lipstick to smear around the vents of all of them except the Easter Egger (you said you only had one green egg layer so she isn't it.)
I would use one color on the RIRs and a different color on the Australorps. Once the next shell-less egg shows up, you will know which of the two groups it came from and then can mark the three pullets of that group with a different color lipstick and hone in on the girl who needs extra attention. You can get leg bands for them and mark her that way or snip the tips of some tail feathers so you can identify her later.
Give this pullet 630mg of calcium citrate daily for a week or until she lays a properly shelled egg.
You can get this at your local WM:
View attachment 3702205
You will give her a tablet of this twice daily to get the right dose.
I would also do the yogurt/oyster shell treatment along with this to get them all in the habit of eating the oyster shell.
The easiest way to give a bird these tablets is to get them off the roost before they leave in the morning and after they've gone up at night, put them on the floor and hold them between your legs to keep their wings pinned then open the beak and poke the pill down and close the beak.
I have had birds that would willingly just take the tablet out of my hand and eat it but they are few and far between. You can try it this way and see if she will cooperate. Or have someone hold her for you or burrito her in a towel. See what works best for you and her.
Good luck.