Plex goes slow while downloading anyway to prioritise?

Hi,

My plex appears to go slow when downloading. I believe its down to if what is downloading on usenet or torrents is using the max bandwidth though I may be wrong. Reason I think this is the case is I upgraded seedbox and this still occured. Is there a way to priortise plex and streaming if this is the case or if its not the case does anyone know what might be going on?

Little bit more detail: Seems to happen worse with usenet so might be linked more than just speed for example when nzbget is extracting. Though what normally happens is plex takes forever to load up libaries and then will not start playing what ever has been chose. Though when nothing is going on in nzbget itll go back to been perfect. The above also happens if torrenting but doesn't seem to affect it as bad and the reason i thought this might be the case is because my torrents don't normally get the same speed as usenet does and usenet often has multiple things queued up when i notice it at its worse.