hens won't lay for a month! what can I do?

[chickenshiha]

For the past month all my hens stopped laying and I'm really confused about why they've stopped because I didn't change anything food or water same, and also the weather is a bit better than before,its a great weather for the past 2 weeks, but in hottest days they used to lay, it's Been 70-80 degrees Fahrenheit, and they're free ranged in my garden I'm always on watch and there's no predators, what's causing it?

 

[limited25]

At about 18 months they go into a molt ... how old are your hens? This is the time of year for molting to occur.

 

[chickenshiha]

At about 18 months they go into a molt ... how old are your hens?  This is the time of year for molting to occur.

one is 2 years old and one is 7 months old and one is 3 years old yeah she mabye a bit old but she was a laying machine! But I don't see any molting it's been a month