Peace lily dying!

[gobblegobb]

Iv had a peace lily for about 5 years now, iv never had any problems with it, until i repotted it a month ago, my mother told me to separate the roots a bit which i did, and ever since it has been slowly on the decline. A couple of new leaves have started to grow, but the rest of it has gone completely lank, i just dont know what to do to revive it again. Has anyone got any ideas to help me save my much loved plant?