Runny tummy and litter question

Hi there. One of my little girl buns has a bit of an upset tummy - the 3 buns usually get one green leaf a day, but the kids gave them 2 the other day and it seems to have upset little buns tum. I will stop the greens until her tummy gets better, but they normally have a handful of dried herbs, pellets and hay in the day. Do I stop the herbs as well and just have them on pellets and hay? I have some plantain being delivered today - wondered if I should be giving them this or just hold off for a while.

Also, I have just changed their straw to regular bales of straw from the farm as opposed to pets at home straw - would this have had any impact - the straw is not as nice, but so much cheaper.

Another thing ... (sorry massive post!). My buns have a wooden nest box in thier hutch and they seem to just use it as a toilet - when we lifted it to clean them yesterday, one side was very wet and full of poo, so have removed the box and put a large litter tray in the corner with some carefresh in it - is this a bit mean .. should I leave the box in the hutch?

What do other people use for litter - carefresh is so lovely and soft but soooo expensive!!

Thank you!

In what way is your bunny ill as it could be serious?

I would take the box out and use a plastic tray. I put newspaper in the bottom and hay on top as rabbits like to munch on their hay whilst toileting. Aubiose is very popular although it's expensive to start with but would last a long time for 3 rabbits.

Hope your bunny is feeling better now otherwise you will have to take her to the Vets.

Her poos are soft and wet, but they are starting to harden up today, so think it was the greens (they are rescue bunnies and I had been told that they were weaned too early and so have sensitive tums).
I have taken their box away and replaced with a litter tray.
Our local farm supplies shredded newspaper bales - do you think that I could use this as a base for their hutch and for the litter trays?
Thanks

Newspaper is fine,

As long as the are getting pleanty of hay and some pellets I would stop with the herbs veggies and fruit until their Tummys are better

Litter tray is great

If the bunny dsnt improve or shows sign of discomfort ie dsnt seem to be able to get comfortable then seeing a vet is important