Sorry to hear you are having trouble. It seems like Delilah is being influenced by her new friend and may possibly be confused by Bentley’s lack of litter habits. The scent of his poops everywhere may be distracting them both from where they should actually go.
The first thing I would try is having a larger (or second) litter box, if possible. Having a bigger one may offer them more opportunities to get it right. Scoop up any stray poops and put them in the box(es) as quickly as possible. I would also clean the first floor really well with white vinegar, which will disinfect the space and remove the scent of previous accidents.
Also, try to notice if they are going more in one area than another. Wherever the bulk of the accidents are, you might need to move the box there. Bunnies often choose their own toilet area, whether we like it or not. You also mentioned Bentley moving hay and having accidents on it. My bunny did this when I first fed him hay as he thought it was a second bathroom. If might be worth trying a different litter (wood pellets, etc.) that cannot be carried away, so the litter box remains the only place with litter and toilet scent.
Good luck!