IMO, a camera with a reflected meter built in is one of the worst possible things for a beginner.
I almost always use the spot meter of my camera to determine the contrast range of a particular scene, but as it shows I still have some difficulties interpreting the reflective values of certain colours. This is something that I'll certainly learn along the way...
I'm looking forward to discover the wonderful world of film developing!
According to the massive dev chart, you should be developing for 13 minutes. Continuous agitation for first minute, then 5 seconds of agitation for each 30 that elapses. You can't agitate for 10 seconds for each minute, you should agitate for 5/30.
The difference between 12 and 13 minutes is 8%. That neg is not 8% off. Additionally, one *can* agitate for 10ag/60sec vs 5/30. People do it all the time. The reason I mention it is because it also does not look to be the source of the issue.
The shots just look overexposed to me. It looks to be printable though.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.