Hyundai Sonata 2006 PO300 codes

I own a 2006 Hyundai Sonata 3.3 V6. Engine light is on, and losses power when accellerated. Full tune-up was done, but problem continues. A computer diagnostic was done and I got the following OBD II codes: PO300 random/multiple cylinder misfire detected, PO301. So at the time the injector one was replaced. After a day it went back to having engine light-on and the following codes PO300, PO302, PO304, PO306. DOes mean I need to replace all INjectors? Is there a sensor that might be causing the problem or something else that you can point out? Thank you