My two rabbits live outdoors in a large run with a litter tray. It's filled with bark and they've always used it for most of their doings. My old lady Lola, about 8 years, sadly lost her sight to cataracts in 2020, which she is coping fairly well with, and is generally fairly fit, still hopping around the lawn (unless covered in snow like now). Since she went blind, or about the same time, more and more poo has been deposited on the paving stones not in the tray. We can cope with that fine, although we're not sure exactly why it's happening, but now it's wee as well. It's hard to clean up rabbit wee on paving stones so I'm looking for options if anyone can suggest any, eg:

Would a very low-sided litter tray make a difference? (the one we use now is about 4 inches high)

Is there anything I could put on the paving to absorb wee that could be easily changed/cleaned? Because they're outdoor, under cover but some rain does get in, it would need to be solid enough not to blow away or get very soggy.

Also the run is a bit 'Heath Robinson' so taking the roof off to get in and clean it is a major job, we do it twice a week and clean the whole run, hutch etc out, but we couldn't get in every day, it would take too long and in this weather it's a bit grim to do.

MTIA for any help