EOS R5 mirrorless file size/quality issue?

[jordaneraines]

I got myself an R5 within the last few months and was having a great time with it for the first month, but around mid-September I started having some issues with the quality of my photos. I am a college student and we have access to "rent" equipment and I frequently borrow (EF) lenses from there. The first time I noticed the issue I was using one of these so I thought that was the problem, because I am almost positive that they are hardly cleaned. I tried it out with my (EF) lens (I can't afford any RF lenses yet so I haven't been able to try that out) and am having the same issues. I talked to my professors and they aren't sure because we haven't had a lot of mirrorless instruction yet. The advice I got was to reset all my settings which I did, and this helped a tiny bit I think but it's still obvious and the quality looks like the file is significantly smaller than it is. I have all my settings set to RAW, and shoot at the lowest ISO possible. I also have a Canon brand lens mount (B&H). I am really trying to avoid sending my camera in to Canon because I need it for classes, so I am wondering if I can receive some help here. 

The main issue I am having is the image quality gets pixely and grainy when you zoom in, but it gets this way zooming in not very far if that makes sense. As in, I should be able to zoom in that far (and more) and not see any quality issues or noise. It seems like the file size is small, and I know it's not any of the software I upload to because I can see the poor quality in-camera as well. Here are some example photos. 

Thanks so much! 

16-35mm lens, ISO 100, 1/250 sec, f/4.5, strobe fired24-70mm lens, ISO 200, 1/125 sec, f/7.1, strobe fired28-135mm, ISO 200, 1/50 sec, f/6.3, strobe fired

[jordaneraines]

I am using EF lenses and have been using them since I bought the camera, which is the only reason I'm afraid it may be an internal issue or something since they looked fine the first couple weeks I shot with the camera.

[jaewoosong]

can you describe your post-processing for your RAW files?  When most new photographers work with RAW files for first time, they often say it looks horrible when compared to the JPG version.  JPG out of camera comes processed with a "photo style" that adjusts sharpness, color, etc. so that it looks pretty decent coming straight out of the camera.  I'm thinking that during the first month, you were shooting JPG and your photos looked ok but after a month, you switch to shooting RAW format.  RAW is straight from sensor and does not apply any processing in camera whatsoever and often they "look bad" or pixelated.

[jordaneraines]

I had a T6 Rebel before this one and I have always shot in RAW (2015). This is why I'm thinking it may be a camera issue because I didn't notice it until fairly recently, and looking back at my first RAWs with this camera they are much better looking in terms of quality or grain in comparison to my newer work. I use Lightroom Classic and occasionally Photoshop to post-process and I never add anything crazy, just maybe some exposure, highlights, and white balance tweaks (and recently, the noise reduction).