Is there a way to tell the age of my chooks?

[McNee Flock]

We recently bought 2 x ISA Browns and were told they were in their first laying season and laying 1 egg minimum a day (we are new to chicken owning) it's now been 4 weeks and they haven't laid a single egg. I have made sure there is a constant supply of food and fresh water, they have clean nesting boxes and a perch they sleep on, not sick as far as I'm aware and no visible mites. They are let out through the day to roam the backyard as they please and peck in the grass.

I have been told that their combs should be vibrant and red, but they aren't, they are dull and floppy. I am now worried that we were sold 'old' chickens that have stopped laying. I've posted some photos, your advice and opinions would be much appreciated.

 

[Mrs. Light Sussex]

There is no way to tell for sure how old a chicken is.
Many chickens will stop laying as the days get shorter. During the annual molt (fall) chickens will not lay any eggs.