XR300 download speed

So Lately I've noticed that a while ago, my internet speeds were going slower and slower... Before I upgraded my internet plan to a faster speed, the problem also occured to me that I was having such low download speeds such as 20mb to 100mb. However, I use to be at 400mb and higher with the plan I was using before. the plan was a 100mb upgrade really but I'm not understanding why my internet speed went down. I tried messing around with the netgear DumaOS site and it hasn't really helped much in this situation... Not sure what I need to do to get my internet speed back to normal. Todays test was also the lowest it got which was 15mb download speed and 2mb upload! It's a shame how I went from 400mb+ to basically nothing. Hopefully this would be answered soon. Thanks for the help community. (The speed test shown is my lowest as of this current post.)