Is deluge blocked by other clients?

[Redsandro]

For a while now I've been experiencing very slow downloads on most (but not all) torrents. Now I've done some network traffic metering, and I noticed I have 40KiB/s of traffic done by deluge, although there's no upload and only 3KiB/s download.

So just for farts and giggles, I installed transmission and downloaded the exact same torrent and found that it was complete before deluge even completed one percent.
Ports are properly mapped, 200 connections are allowed, everything else seems to be fine leaving me wondering: Is deluge blocked by other clients for some reason? Do I get 30KiB worth of handshakes and are they all denied?

[Cas]

Sometimes private trackers have in the past arbitrarily banned versions but not aware of that with latest 1.3.3 release.