Fortigate doesn't display the saturating applications in fortiview

Hello,

I've a newly deployed Fortigate 200F in my LAN. I've an internet souscription bandwith of 16M.

Recently I've been realizing that my bandwith is constantly saturated, but Fortiview doesn't show me the applications that saturate the bandwith.

As you can see on the images above, the total bw of the internet applications displayed by the firewall (4Mbps) is much lower than our subscription (16Mbps) but it still displays our bw saturated, and the internet service is slow.

Please note that this is not permanent. It happens constantly.
When look to the security report, the firewall doesn't indicate any malicious attack.

Please any help will be very appreciated.

Thanks