I have a Deco M5 and 2 Deco M4s in my network. 
 

i want to configure them as a chain with the M5 as the main unit at one end and then one M4 connected to the other M4. However when I set up the system both M4s connect to the M5. My house is a L shape so the second M4 has a very weak signal. How can I configure the second M4 to connect to the first M4? I cannot move the M5 to the middle of the house as the fibre optic cable is only available at one end. 
 

thanks for any help