Egg laying question

[Kirkat34]

I have 6 Isa browns & one leghorn, all are 15 weeks old as of this past Tuesday. I've already found five eggs from four the Isas and I'm wondering if this is normal...not that I'm complaining - I'm eggstatic over getting eggs already. I'm just wondering if it's normal when everything I've read is saying they don't start laying until around 18-22 weeks? In the attached picture, I'm assuming the middle egg in the top row is from the same girl that laid the egg to the left of it, since it a bit bigger and the rest were found yesterday, today and are smaller.

 

[Homesteadermomma6382]

Are you sure of their age?

 

[Kirkat34]

I got them from TSC the day they were delivered and was told they were 1 - 2 days old. I'm pretty sure they aren't more than 15 weeks but I'm not positive, just going by what they told me

 

[GC-Raptor]

Wow, my ISA Browns are eggsxactly 5 weeks behind yours, 10 weeks last Tuesday, also from TSC. I got them on a Thursday, same day they arrived.
I'll expect eggs in 5 weeks.
My first Flock (Golden Comets) started to lay at 16.5 weeks.
I've heard of red sex-links starting to lay in the 14th week so I'm not surprised.
Leghorns can start around 16 weeks.
As for the larger egg, I would say it's the second egg from a pullet.
My Golden Comets eggs started at 42/43 grams and quickly got to 70/71 grams and 80 grams common.
Here's my new girls.

and my 22 months old Barred Rocks.

GC