Marshmallow Problem ?

[TkSilver]

It could be different drivers for your hardware or the OS using a different amount of background system reasources.

After doing a quick google serch it does look like other users are experiencing higher memory usage and some battery drain issues after updating.

If you have a convienient backup of everything in your phone I would recomend doing a full power off and on cycle first and if that does not help then a hard reset might help.