I have a Deco X55 system with 3 devices.  My 2 points only have a "Fair" signal, but all devices appear to connect to these points and work ok.  But I'd like to improve the signal to these 2 points if possible. 

Unfortunately I can't improve the signals by bringing BOTH the 2 points closer to the router, and also can't move the location of the router itself. It is possible to locate a 3rd point in-between the 2 points if that might help.  I would have to purchase that additional device.  My question is: Would purchasing another Device (creating a 3rd point in-between the router and the existing 2 points) improve the signal to existing points?  I'm not a networking expert and I'm not sure if points can (or ideally should) be Daisy-Chained in that way.  And even if the signal to the existing 2 points can be improved by adding a 3rd point, I'm guessing the speed of devices connected to those farthest points might be worse having to go through another hop to get to the router. I'm trying to avoid purchasing another point and discovering it made no improvement. 

Thanks in advance for your assistance.