I have some 26 weekers with no eggs from them yet, either, but they are Sultans so I wasn't expecting much. My average has always been around 24-26 weeks; hopefully, you will see eggs soon.
What breeds? Some of them are later than others. I had several "production breeds" that didn't start until 26 weeks, but then some of the Easter Eggers didn't start until 28 1/2 weeks. Are the combs and wattles bright red? Any squatting? Are they vocal? Have they started investigating the nest boxes?
Just shy of 26 weeks here... no eggs yet from my black star nor my aracauna. My leghorn/orpington has also stopped laying since having a broody spell that lasted a couple days... about 2 1/2 weeks ago. Everyone's comb is brightening up, so hopefully sometime before spring, I'll have some eggs...
Our chickens are right around 26 weeks old and still waiting on our Silver Laced Wyandotte, Blue Andalusian, New Hampshire, and one of our Black Australorps to start laying.