Since she's young and she's relatively new to your care, give her a few more days before worrying too much. Stress can cause an excess of porphyrin. However, if it continues, I'd suggest calling a vet to make sure it can't be illness.
A few other reasons there may be excessive amounts of porphyrin is dehydration or a poor diet. Make sure you have at least two water bottles and at least two bowls (that can't be tipped over) of water. As for food, I'd recommend Oxbow adult rat food with veggies as supplements. It may also have to do with the air quality. Please make sure you aren't using lotions, or fragrances with your rats.