Brittney, this is so heartbreaking! You lost Marlow, now Charlie has soft, sticky poo...
I hope your chins do not have Giardia and maybe Charlie just misses Marlow!
I've read that chins normally harbor giardia species in low numbers, but when a chin has lowered immune system or stressed, then parasite uses the 'opportunity' to multiply.( So it's not necessarily contaminated food, hay, water).
Couple years ago my chin got diarrhea (and it smelled bad) when I was away for 2 weeks, my husband was taking care of him, but it was too stressful for him without me! He was tested for giardia, result was negative,who knows maybe it just did not show up? Just to be save I decided to try homeopathy, wild oregano oil and it helped. I saw improvement in 12 hours or so! Later I found an article on chincare.com about using it to treat giardia, so you can read it if interested. It helped a chin who went though weeks of panacur treatment and Giardia still persisted. "In 1999 researchers at Cornell University discovered that wild oregano killed every germ against which it was tested. it has anti-fungal, anti-bacterial, anti-viral, and anti-parasitic properties, rendering it one of the most potent germ-fighters known to man."
Of course if your chin has Giardia, you do not want to risk it, it's better to give meds the vet prescribes. But it's useful to know about oreganol if treatment does not help.
Giardia is often missed by vets is they use the wrong type of fecal flotation.The most reliable way is to use zinc sulfate solution.
"Slides should be examined within 10 minutes of preparation because the cysts may begin to shrink. Because animals shred Giadia on an intermittent basic, it is recommended that a series of zinc sulfate concentration tests be run over 3 to 5 days to maximize chances of accurate diagnosis". So, it's great that the vet will have the results only on Tuesday.
Also if your chin does have Giardia it's also recommended to wash chins hands and coop cups often and to change bedding at least once a day.
And I would contact the seller to ask about the feed.
I am so sorry for your loss