Ummm download speed and upload speed are only a small factor in pings really.
Thats PLENTY of bandwitch to ping a couple of servers. the ping packet for each server is only 11 bytes, so for 24 servers thats 264 bytes. Not even 1KB downloaded.
Pings can be affected by distance, line quality and other things. Also depends if your upload is being hammered while pinging the servers.
I would go to speedtest.net and run a test there and see if it matches what your other test.
Should also install something like DUMeter to see if something is eating your upload.
Another possibility is that you've been put on a low priority traffic band. Some ISPs do this when you download too much data. Mine does this if i download more than 1.2GB between 4pm and 9pm
it really sucks