different IP addresses

I'm new in the Network world so I'm still trying to figure things out. I have a server with an IP address like 192.168.1 etc. There is other devices that communicate and share information with the server, all of them are DHCP enabled and the IP address is also something like 192.169.1.etc. but sometimes they reset after power failure and change the IP to 169.254...... so i lost communication from the server with this devices. why this happen and how can i fix it?