As tunnelrat points out, a smooth bore could have hit the target at 8 feet ad OP is talking about large misses.
Again, I want to point out that I'm not trying to criticize the OP, and I may not even be right in my assumptions because I don't know OP and I haven't seen the guns in question.
From 8 feet, with 2 different examples, regardless of how dirty the guns were they should hit no problem. The difference between being fundamentally sound and being able to hit with technique throws off a lot of shooters that haven't had individual training somewhere, and many haven't because paying for training is pretty darn expensive much of the time. This results in a lot of shooters that can hit what they're shooting at with the guns they're used to because they have technique that makes up for their lack of fundamentals with that gun.
The most common example of this that I've seen is with grip and trigger press. One of these is a technique, the other is fundamental. Your fundamentals are the things that allow you to shoot accurately regardless of what gun you're holding, techniques help with other things like recoil control. Many people that I've seen can actually compensate for underdeveloped trigger press fundamentals by adjusting their grip. For example, if you were to lock down a gun super tight in a vice so that only the slide could move and lined it up with a target, you could jerk the trigger like crazy and it's still going to hit. Likewise, if you have a good grip for a gun you're used to (and you should) then you can often land hits with it in spite of not spending enough time developing trigger control. This will become evident when, for example, you pick up a subcompact that takes a different grip technique and squeeze the trigger as you normally would and get different results to the left of your target which happens often with newer shooters that need to learn trigger control.
So, without being able to surely diagnose this as the issue because I am not able to witness what is happening in person, I would recommend that as many people as possible look further into fundamentals vs technique and supplementally look up Jeff Cooper's video on "surprise break." This should go a long way for many because, from what I've seen, most shooters have developed their gear and their technique to a much higher level than they've focused specifically on their fundamentals because in many cases the difference in fundamentals and technique has not been explained to them.
I hope this advice helps. The only other thing I could say is to get pics of the guns, but I highly doubt hats the issue. I've been guilty in the past of blaming gear for my lack of fundamentals as well. We are all guilty of it at some point in time. Sometimes we even do it when we know our fundamentals and are just having an off day. It happens. Maybe it was the guns, but the odds are greatly in favor of it being something the shooter can fix with the advice above.
Edit: Doc, I did say I don't know you. I didn't call you a novice and didn't mean to offend. However, the odds are still in favor of you needing the advice in this post because the likelihood of 2 range guns being the problem is just extremely low. I'm not saying that you can't shoot your guns accurately or making any wild accusations. I'm just saying that in most cases, with most shooters, the advice I posted here will likely fix the issue. Again, you were shooting to the left of the target. This is extremely common with shooters who don't have their trigger press down yet. As I mentioned, I haven't watched you shoot in person, but most of the time shooting left is a common issue with shooters in need of coaching. Based on your post alone as evidence of what could be wrong, if one is playing detective then the most likely scenario is what I came up with. There's always the less likely chance that 2 rental guns had problems, but it's significantly less likely in most cases. If it were me and my fundamentals weren't good, I think I would probably want to blame the rental guns as well. It would feel a lot better than saying "maybe I should recheck my fundamentals." I find it hard to be critical of myself just like anyone else. You don't have to tell me I'm right or anything, but if you'll keep my advice in mind and humor it just a little bit by looking up the stuff I recommended, even if you don't stroke my ego by letting me know you checked it out, then you'll be doing yourself a favor and you'll walk away with some extra knowledge (or perhaps a refresher).
I don't mean to come across as "lecturing." I'm just trying to throw out something useful since I can't find the exact issue through text either.