People go back and forth about messing with the humidity. Some say more humidity is good, some say more is bad. I would say don't mess with it since the jury is out on it. Bumping the temp a couple degrees is a good idea because it augments the immune response.

Signs of RI:

Popping or wheezing sounds (put your ear right up to the bp's face if they are not biters)

Bubbles around the mouth or nose holes or mucous in the mouth (open the mouth with the aid of the "bar" of a q-tip. don't even think about sticking the cotton part in there, but the bar can help pry the mouth open so you can get a good look)

Lack of feeding can signal an RI, but of course that could be for any reason. If they are eating steadily still that's a good sign that they are pretty healthy in my opinion.