My female Netherland dwarf is about 9 months old, and I’ve noticed over the past month her urine has been very peculiar. I’m a first time rabbit owner and Undertale is my only rabbit. She’s been producing very thicky and sticky urine, when moved around it almost acts like slime, its stringy when pulled apart and often gets stuck to my rabbit’s bottom. She does one of these sticky pees about once a week, and the other day I noticed her urine was very dark red, almost like blood but not quite, otherwise she has light brown pees and some dark brown pees. She drinks plenty of water (she has two sources, a water bottle and a water dish which she uses both) and I give her 2 cups of leafy greens a day (lettuce mix with spinach) and some pellets in the morning. She always has fresh hay and hasn’t had any issues going to the bathroom, though she did pee twice on a new bed I got her, thus prompting me to bring her to the vet and the vet said she seemed fine and healthy and told me I was doing a good job. But her urine still concerns me, but I don’t wanna jump the gun to take her to the vet again as that can get expensive. They never did a urine test on her because her only symptoms are the discolored urine. She’s super active and happy and normal otherwise. I just want my baby to be okay! 
I’ve attached some photos of her litter box and some of the stringy urine that followed her out of the box today;
https://imgur.com/a/6SffvNr
https://imgur.com/a/LM1DkHT
https://imgur.com/a/PcxTr30