Xfinity X fi pods not giving consistent speeds.

I have gig speed internet with 2 xfi pods placed in 2 rooms on an upper level from where the main gateway is located. I have been having issues with the wifi signal for the pods varying in speed consistency. it will work fine for a wail with speeds of download 75 to 150   then all of a sudden drop to download speeds of 0 to 5 sometimes completely disconnecting for 1 to 2 mins then it comes back up to the 75 to 150 speeds. any ideas on what would be causing this? 

I have tried resting the main gateway witch will resolve the issue for a short time.