"输了几个很好的代表？” means a council gambled with their great representatives,then they lost.
"this year my school's student council lost a couple of great representatives"
Most of the time,We can use 失去 for lost。but 失去 indicates some bad conditions. “What happend? politic conflicts or death”。
add an explanation.
After more consideration,
I think it is better to use either of the two。
失去 means something lost which you wish did not.If you were sorry for the reelection ,you could use 失去。