Alright everyone I figured out the real cause and since I haven't found a definitive article online, I decided to narrow it all down here for future reference, since some Nautilus Mini users might(probably will) encounter the same problem.
If you get an unpleasant taste, low vapor production, and if also the attachment ring heats a lot (the one that connects the tank to an ego battery) you HAVE to change the atomizer, everything will get back to normal, I just did it and my ecig is back to being perfect again.As Rwb1500 said, do NOT clean the atomizer, it also says so in the manual, cleaning it won't make ANY difference, so don't even bother trying it. Since the atomizers are indeed cheap (I bought 5 for 3.50 euros at my local smoke shop) the change won't cost you a lot (as LMS62 correctly stated).
tl;dr version:
IF you experience any of the following:
Unpleasant taste (Mostly metallic with a hint of a bitter)
Low Vapor production (or inconsistent)
The ego cone (the ring that connects the battery to the tank) heats a lot
possibly the airflow adjustment ring heating too
Then CHANGE the atomizer. DO NOT clean it.
Also, I noticed that my battery now lasts longer, I've been vaping for 2 hours straight whereas before I could for 1 and a half-2 hours tops, but that might not be true for everybody.
In general, an atomizer lasts for 4 to 6 weeks depending on your use, for heavy vapers it might drop down to 3 weeks or a month tops.
Have a good one everybody.
EDIT: Also, a "healthy" atomizer makes a loud hissing/crackling noise when you click the battery, if it makes a subtle sizzling noise most likely it needs changing.