@damian.niolet 

When using mulitple Range Extenders the most important thing is deployment.  Espically if you are cloning the SSID from the main router.  

1.  Then need to be linked to the router, and not to each other.  While "Daisy Chaining" is techincally possible it is not recommended due to speed and connection issues that will result from it. 

2.  They should be placed on opposite ends from each other.  When using mulitple range extenders you ideally want the router centerally located and the extenders in opposite ends of the home.  This is to eliminate the possiblity of conflicting signals

3.  They should be postiolioned with in a good signal enviroment from the router.  A range extender can only extend the signal they recieve, so if its a poor signal they will send out a poor signal.

If any of the above is not possible there are two options you would want to consider.  1.  a wireless powerline kit  2.  a Mesh networking router system.  

Best Regards