Not until their wattles and combs are fully grown. Are they squatting yet? By the looks of things you have alittle bit longer to wait. Its really the worst part of the whole process. Good luck!
I'm hearing that its been later and later this year. So your probably looking at maybe a month but, it could be sooner if they start squatting.
My friend's light brahma just started a few weeks ago - she got her as a chick in February. I was out there visiting and remarked on her red comb and wattles - to keep an eye out she might start laying soon. The next morning, she laid her first egg! She's laid an egg everyday since then. I wonder if hens that start later are more regular early on than those that start early? Now my friend thinks I actually know something...hahaha Brahmas are supposed to be good winter layers, so don't worry if yours starts later than sooner. You should have a good supply from her through the sparse months.