Hey Renee,
Those congested, grunty noises that Janny has been making are definitely the sounds of a respiratory infection. As you probably already know, rats carry a pleomorphic bacteria in their lungs and tissues called Mycoplasmosis or Mycoplasma Pulmonis.
Here is a link from the Rat Guide on M. Pulmonis:
http://ratguide.com/health/bacteria/mycoplasma_mycoplasmosis.php
Unfortunately you won't be able to properly treat this infection without veterinary intervention. Infections involving M. Pulmonis, if left untreated, may lead to serious lung scarring, pulmonary abscesses or pneumonia. I would strongly suggest that you take her in as soon as possible for a visit with a veterinarian so that they can prescribe Janny antibiotics to treat the respiratory infection.
Treatment is time sensitive to prevent the infection from advancing otherwise it is very likely that what was an upper respiratory infection will develop into pneumonia. Time is critical and since Janny has been symptomatic for 3 days, she needs antibiotic treatment as soon as possible.
Typically vets prescribe two antibiotics that work synergically called Enrofloxicin (Baytril) and Doxycycline (Vibramycin). Baytril and Vibramycin are typically dosed at 5mg/kg - 10mg/kg twice a day for at least 6 - 8 weeks. Some vets will only prescribe a 14 day course but in my experience respiratory infections aren't completely cleared and it may return if antibiotics are not given for the full 6 - 8 weeks.
Please make sure that you get her in to see a veterinarian as soon as possible so that her respiratory infection doesn't worsen and she can make a full recovery.