Weird sudden hiss coming through my mastering chain

Been suddenly getting a weird hiss from my mastering chain (that I have not changed whatsoever). I have been using this for ages and I'm getting this persistent hiss on my master. I checked to see if it's my headphones and its not because I opened other project files and it's not happening. I muted everything on my mastering chain and noticed my bass booster is adding the hiss. I'm literally hearing the hiss while the project/track is dormant though? I rebuilt the mastering chain and it's still happening and all the tracks I have mastered with it and rendered with it are coming out witu this hiss. I have used this chain for many, many tracks with very little alteration and have never had this issue. It's really strange. It would've been far more noticeable and prevelant previously too because I was using it to master hip hop tracks with vocals whereas now I'm using it to master electronic/ambient type tracks. Especially considering I'm hearing this hiss when the track isn't even playing. I have opened regular project files and implemented this plug in and there's no hiss whatsoever. Even when it's turned up full blast? Where as its implemented pretty subtly on my end. When I mute it, the hiss is virtually gone. Ive reset it to the default preset also to no avail. Any ideas what the hell this could be? I can describe my chain if needs be later on. Not currently at home.