The red ruffed lemur, and the golden lion tamarin/sloth/green aracari exhibits were both empty and had paper covering most of the window. All the animals except the green aracari were signed at the exhibits outside in the back. The golden lion tamarins were back there back in July, but the others weren't. I don't know anything and there wasn't anybody to ask, but I'd guess they're doing some kind of work in those exhibits, otherwise why cover the windows in paper and not just put "nobody home" signs in the exhibits? Somewhat interestingly the sloths were signed in the same exhibit as the red ruffed lemurs (which is the old black howler exhibit) and not with the tamarins, though I didn't see any sloths.
The two indoor exhibits are being worked on. Two weeks ago they had the red ruffed lemurs paired with one of the sloths, who stayed in the crate in the exhibit. A week ago I noticed the door to their holding area was opened and one of the sloths was hanging out back there. I believe it's the male sloth, Vlad, and I am guessing that their female sloth, Athena, is behind the scenes. It might have changed since last week, but the aracari was in the two male tamandua exhibit then.