Need help

[Vsop]

I've got ADSL 256 kb/s. My first Bitcomet torrent was a movie with low number of peers (about ten). Despite of that my download speed was 30kb/s. Since then I've downloaded 4 torrents, with many peers, but every time when I've started to download another torrent, my dl speed was descending. Now, I'm downloading a very popular torrent with 812 peers at 12, 10 kb/s. Of course, I'm seeding the torrents I've downloded, (but not when i'm downloading). Can anyone tell why is it like that, maybe because of the settings? Thank you guys in advance.