Hi Darlene,
Unexplained muscle mass loss when stools and appetite are normal is almost invariably due to Yin deficiency. In this dog, it may be bordering on Empty Fire, in which case the warming and partially drying ingredients of Rehmannia 11 may have been mildly aggravating, or at least inhibiting any sort of improvement. Blood and Yin deficiency is also usually signaled by a response to DHJST
Yi Guan Jian is the basic unexplained weight loss formula. Where there is a suggestion of perhaps neuropathy occurring in response to Yin deficiency and Empty Fire, I reach for Zhi Bai Di Huang Wan. I'd probably start there, or you can use the two in tandem. If you're on the right track, you should see some return of strength over the next two to three weeks
Hopefully that helps you out!
Steve