Is my rat ok? She's a baby?

Ok so on Friday I got 2 new rats. They play fight a little bit and sometimes one doesn't sleep in their igloo, which worries me that they aren't getting along. The one rat is very playful but she made a kind of chirping noise when I pet her earlier. It stopped about 30 seconds after I was done petting her but when I gave her some dried papaya she did it again for about 15 seconds. Should I be worried? Oh and she also has a little bit of fur sticking up but she rubs against the water bottle sometimes so I don't think I should be worried about that...right? If you can answer either question I would be very grateful:) thanks:)