My female yearling has got me scared. Just a few months ago she was weighing in at a reasonable 400 g

Now she's roughly 270 g, making me highly concerned and hoping that my scale is just broken. She's 11 months old now, thicker than an adult mouse but will not eat anything larger than a hopper that maxes out at 12 g. If she eats anything larger, she will regurgitate or stress her cloaca to the point of bleeding. She's 25 inches and I'm very concerned that this phase will permanently stunt her growth. She does not feel thin and she is still rounded but not as plump as before. I usually feed her on a weekly basis. Today I will start offering her 2 hoppers in hopes that she'll fatten up. I've never had this problem with any if the other snakes I've had. Has anyone else encountered this problem? If I have to I'm willing to breed gerbils (already keep them as pets) if it means getting her back to a healthy weight. Recommendations?

Took these pics yesterday. She otherwise seems healthy.