What might be the issue with my car? will a fuel injector cleaner caused this is

What is your question?

I have a honda civic 2000 lx. The engine light came on right after filling gas "full tank". I also added a bottle of redline fuel injector cleaner before filling the tank. The engine light came on right after i left the gas station, just a few yards away. I stopped and check the gas cap and it is tight, i made sure to hear at least 3 clicks. Also, i took fuel cap off and put back on and rotated it a full circle just to make sure it is very tight and secure. The engine light still on. I used my OBD2 reader, and getting "p0301, p0302, p0303, p0304, and p1399". I looked up the codes and i got: P0301- Cylinder 1 misfiring P0302- Cylinder 2 misfiring P0303- cylinder 3 misfiring P0304- cylinder 4 misfiring P1399- Manufactures control Ignition system OR Misfire A rep at a local auto parts store advised it could be something related to EGR valve having clogged ports. It may need to be cleaned or replaced. Or it can be the spark plugs? What things/parts I should ask the mechanic to check? I am newbie when it comes to car fix. Any advice is appreciated, thank you.