True diarrhea (where the fecal poop is watery or pudding like and it's not just the cecals coming out pasty) and stomach bloat are both an
immediate emergency and you need to get your rabbit to the vet without delay. There's nothing else to do.
True stomach bloat is extremely serious and can cause stomach rupture or cardiac/respiratory arrest if not treated promptly. Syringe feeding a rabbit with stomach bloat is contraindicated and could prove very harmful as it increases the stomach pressure which is already causing serious complications.
Medirabbit: bacterial enteritis
(WARNING: link contains extremely graphic medical related photos)
Medirabbit: weaning diarrhea (described in young rabbits, but elements still applicable to adult rabbits)
And if there's the pathogenic bacteria clostridium involved causing the diarrhea, this can be fatal in a very short time without the proper meds metronidazole and questran(cholestyramine), and some IV or sub q fluids. Activated charcoal or kaolin may be used in a pinch in place of questran to bind the bacterial toxins, until the bun can be gotten to the vets, and good hydration to accompany the med or supplement is also important as it absorbs fluids,
but getting bun to the vet right away is absolutely essential. I know there's a vet good with rabbits at Twickenham Vets. They might be the closest to you, or check the list to see if there mght be another closer.
https://rabbitwelfare.co.uk/rabbit-...abbit-friendly-vets/rabbit-friendly-vet-list/