4 weeks is nothing for an animal that age wait until she decides to go of feed for 3,6,9,12 months

Do you have a weight on that animal?

If could be various things such as what we call "the wall" which is why I ask abut weight, husbandry, catching up to compensate with over feeding etc.

You can do a few different things, change the enclosure, change substrate, downsize, lower temps etc, to see if anything triggers her back but most importantly it's about PATIENCE, they are efficient and that is just what BP do sooner or later.