FortiWifi 60D Internet Bandwidth Issue

Good day all, I have a Fortiwifi 60D, everything is running great however we recently upgraded our incoming internet to 300DN/20UP. When connected directly to the internet gateway I get the expected 300MB down and 20MB up using a speed test. When connected on the LAN side of my FortiWifi 60D i'm getting max 100MB DN and 20MB UP. 

Any idea why it seems to be capping at 100MB down?

Any advice is greatly appreciated!

Thanks,

Bob