Slow internet for users - Firewall Security profiles?

[alladas]

Our users having internet slowness issues for a certain time frame. One group of users had this issue last weekend ad it's working fine now. Yesterday and today we have another set of user machines having the same issue.

For me the question is that: all the users use the same port on the firewall for internet traffic. Why is that certain users having issues and not others? 

I've checked for the firewall policies if any policy is hindering the speed or something, but I don't see any policy slowing the internet speed. Has it to do anything with the security profiles? As I see my previous Network person designed few security profiles for DNS filter, Web filter and Application control profiles. 

Any inputs appreciated. 

Thanks.

[packetpusher]

Maybe you should correlate the slowness with other events on the LAN. Perhaps someone is syncing iTunes library, others are streaming video, etc. Also, some employees are likely to be to a wireless and others to the wired network. A packet capture will be needed in order to dive deep.

[Santiagomunoz]

I have the same problem, when I activate filtering policies the internet of the user gets too slow, I have a fortigate 90D and it happens to me when I want to do the filtering to block navigation to the users