At a dead end with diarrhea

I'm going through the same issue with my 5 year old beardie! She keeps having very loose stool, quite smelly too. I can tell right away when she has gone poo. Has been tested twice for parasites but came back negative each time. I've tried switching greens, more bugs less salad, removing certain veggies. Nothing seems to be helping. She acts normal but I just feel like having such runny stool cannot be good!

I just bought some probiotics to give a try, here are the links to two I would recommend trying. The first is the one I bought that is actually quite cheap and the second is more expensive:
https://www.beardeddragon.co/index.php?route=product/product&path=61&product_id=280

https://www.amazon.com/Nutribac-Dietary-Supplement-Reptiles-Amphibians/dp/B0058DVVAM/ref=sr_1_3?crid=2WTE88W6RK1RA&keywords=reptile+probiotic&qid=1568355715&sprefix=reptile+prob%2Caps%2C212&sr=8-3

Also got some bee pollen powder. Lots of people sprinkle it on their beardies veggies. It's naturally packed full of super healthy stuff like amino acids, antioxidants, etc. You can buy it off the same website as the first link I provided. Hopefully this helps!

Just to update everyone, and anyone who stumbles upon this, Xena had her first log poop in about 2 months!
I truly believe it was the light fixture. I updated from a zilla slimline fixture and bulb to the zilla slimline fixture mounted inside her tank (with the plastic lens removed) with a reptisun tube instead and in about a week and a half she had a normal bowel movement.
Thanks so much to everyone who gave suggestions. Our girl is on the right track to getting better!

Her new tank setup:

That's great ! Always happy to hear a good update. The lower temps. probably helped out as well.

Thanks for the update! Always great to hear things worked out.

-Brandon