Stress causing dirty bum?

When I checked Malt today I noticed he was really dirty around his bum and there was quite a lot of soft poo in his hay that he'd obviously been sitting in. I washed all the stuff off him and cleaned his hutch out but it's not normally like him to have that much around his bum. He just moved into a new hutch on Monday so could stress be a possible cause? There's been no change in his diet so I don't know what else could have trigged it. Also last time he went to the vets about a month ago she put some Rearguard on him but I'm worried I've washed this all off by cleaning him. Will it still be effective?

Stress can cause all sorts of digestive upset, so yes it is possible, but i'm wondering if he has had this before if vet has put rearguard on his bottom? It could be that his diet needs a little adjusting. Is he well in himself otherwise? eating, drinking, doing normal droppings as well as the excess malformed caecotrophs (sticky poo)? If he seems unwell overall then I would take him to your vet asap.
If all else ok then it would be worth withdrawing his pellets for a few days and feeding just hay and water until his tummy settles down a bit. What do you feed him? does he have access to fresh hay? are you sure he hasn't had too much of one particular veg or veg gone a bit yellow? Or too much grass too quickly?
If not clearing after a couple of days of just hay and water then he will need to see your vet anyway, certainly have his teeth checked as well, sometimes discarded caecotrophs can indicate dental issues.
Vet might give him a probiotic or suggest a change to his diet - more fibre and less pellets in the long-term.
It's really important that he's fully dry and warm before he goes to bed, especially if he lives outside. Hope you can get it sorted soon

if it's once or twice, that's okay. He could be producing too much sticky night time poo. if this is onging I would keep a hay only diet

It happened a few times last year and I mentioned to the vet who said he needed a diet change (from mixed food to pellets) and he's been fine since. She did the rearguard last summer just in case and when I took him back last month my mum asked if he could have it redone because I think the vet scared her last time! He's been completely fine otherwise, just getting used to his new surroundings which is what I thought might have been the problem. It's been a bit of a turbulent week for him (had to move him twice, from old hutch into spare hutch and from that into his new hutch) so I was hoping this would just be a bit of nervous adjustment. I'll keep an eye on him and if it happens again I'll take him to the vets. Thank you!

You could also try some Fibreplex to try to get him back on track.

is his diet compose of 90% hay?