How Much Fussiness in a 4 Week Old is Normal?

I have twin 4 week old daughters. One of them is never fussy and only cries to let us know she is hungry, needs a new diaper, etc... my other daughter seems to cry so much more. She can be full, dry, and not in any pain and still scream her little head off. She isn't colic, but she does cry on and off throughout the day when she isn't sleeping. Both my daughters are supplimented with formula because I can't make nearly enough to feed them both. They take the Gentle formula as they both spit-up often. These are my first children and I just don't know what is normal. Also, any ideas to calm her down? She hates her bouncer, sometimes just holding her close helps, but not always. She only takes her pacifier half the time. I'm getting a swing to try tomorrow. Help?