Anything that can go wrong, does go wrong, and you don't want to be a deer in the headlights, you want to have someone in your corner that has seen it all and knows how to deal with all the hurdles that come. 

So, I think it is likely that any individual resident suing me would result in immediate lis pendens for everyone since they've operated as a group in the potential wrongdoings here.

You can never go wrong doing the right thing! 

People can sue you even if they are wrong.

What could go wrong?

Even if this weren't the case however I would still keep them separate just for an easy paper trail and to avoid any appearance of wrongdoing.  

What am I doing wrong?

Is that wrong?

If the new flooring was installed wrong do they owe you an entire new flooring?

It will help cover everyone in the event something does go wrong.