Hi Sonya,

The ideal size is around 20mm for trigger...they normally grow about 1-2 mm per day and FS would wait until the small ones to catch up for trigger so that you can have the best result...

I was in the similar situation like you dozen of small ones between 10-14mm and only one big ones, I think it was two days later I had my trigger and I got 15 eggs out of that...yours look like well on track, congrats!

Hope all goes well and keep us posted.