mahaba ang explanation for this but basically its perfectly normal na kahit maraming seeds, mabagal ang download speed
short explanation. just because you are seeding a torrent it does not mean you are actually uploading at full speed. its possible the seed is also downloading/seeding other torrents so their upload speed is divided into how many torrents they have running. so kahit na say 10mb/s ang speed ng seeder, if he has lots of torrents running, it could mean he is only contributing like 10kb/s to that torrent that you are downloading. and as such kahit pa 10mb/s ang speed mo, if the seeder is only uploading at 10kb/s you will only get 10kb/s