I too, had chronic soft poop in my pup.
Is it a bit of a yellowy colour?
I'd had her tested for giardia at 3 months of age, came back negative, but things went from bad to worse, checked again and lo and behold, she had giardia. (She's 8 months old tomorrow). she seemed to fluctuate, things would look like they were improving, then it would be bad again for a while.
She just finished her meds, which made her poop even more loose, but they are a brown colour, not yellowy like before. I'm hoping now that she's off her meds that her poop will firm up.
If not, I'm going to take her in next week and test for SIBO (something you might consider) or EPI.
Good luck, I know how frustrating it is!