When you say: "turn red" do you you mean in the µTorrent client? I am currently experiencing this, I have about 50 torrents seeding and different ones will alternately go red, then fix themselves while yet a different one that was working will turn red, it seems to be completely random. I wasn't sure if it was a µTorrent specific problem or with the tracker, either way I have been baffled
The issue you are witnessing is most likely just an adjustment in your µTorrent client and can easily be fixed.
Open your µTorrent Preferences choose 'Queue Settings' and make sure that the value of
'Maximum number of active torrents' is higher then the amount of torrents you want to handle parallel (up- and download).
Save your new settings and you should be fine.
Hope this is of any help,
Gerald