I have got U/L capped at only 25% of my total bandwidth.
Remember that DSL connections are usually "asymmetric".
For example my modem/router tells me my downstream bandwidth is 20Mb/s but my upstream bandwidth is only 1Mb/s.
So my upstream bandwidth is only 5% of the total.
If you have capped your uploads to be 25% of total bandwidth, that is way too much and your upstream bandwidth is being saturated by your torrents. So set it to something like 2.5% of total. You should see an improvement.