Quick update on Kiya, hope this is helpful to others dealing with similar issues:
We had a full blood panel done for parasites, kidneys, thyroid, liver function, etc.. also a TLI test for EPI and a urine test. Still waiting for the gut test results from (animalbiome.com).
While waiting for test results, and since all the signals were pointing at EPI, we started her on an enzyme supplement (BioCase Plus), which is enzymes + probiotic + b12 supplement. Something a lot of people successfully use for treating EPI dogs according to the EPI FB group. To our surprise after 2 days of supplement, liquid poop firmed up a bit and for the first time in months, she had solid poops (not consistently solid, but also not as liquid as before and not needing to go out every 30 min).
Fortunately and unfortunately, the EPI test came negative, her TLI was fine, and her liver functions were fine, no thyroid issues, but her proteins+b12+calcium level was very low, which supports the weight loss of 5lbs in two months. The vet diagnosed and decided to treat her for PLE protein-losing enteropathy and said we should continue BioCase Plus as it's probably helping her pancreas, which in turn helps other body functions.
She had an injection of a steroid (dexamethasone) and is on prednisone to ease her GI inflammation, also she is eating Hills Diet Biome prescription food right now + taking b12 + calcium supplement. It seems like she is doing better (no major diarrhea) and is less anxious, but time will tell and we will see if she starts gaining weight over the next few weeks on this new prescription diet.