SO - to follow up: Vet tested my mareās ACTH, it is down quite a bit from first test, but not normal. Her options were to 1. Increase the dose by 1/2 pill OR 2. Try Smart Pak pituitary pellets - this vet has had some success with these helping the horse and delaying the need to increase the prascend. So I decided to try the pellets, they will start tomorrow. She is still somewhat short in front, even on the equioxx but also generally still a bit āblahā unless you have treats or its time to go out. With the modest increase in her feed, vet thinks she is looking a bit less ribby, but didnāt expect that to be fixed in a week or so.
The concern I had at first, that the prascend wasnāt helping was apparently unncessary worry as her #'s did improve.