The combination of the vet visit, the change in litter box and the fact that your bunnies were pent up for a longer time, is probably the reason that your bunny is quieter and not herself.
skyblue is correct about 10 weeks old maybe being too early for greens/veggies. Most people suggest waiting until a bunny is 12 weeks old. You have to start slowly and only give one veggie a week, then the next week you can try a second veggie, and so on. And, spinach is one of the veggies that should be limited. Here are 2 good articles on veggies and which should be given less often:
http://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
https://binkybunny.com/BUNNYINFO/VeggieList/tabid/144/Default.aspx
As your bunnies mature, you may have to separate them until they have been spayed. Once the hormones start up, that can bring aggression. Rabbits can fight and can severely injure each other. That is not a given, but it is certainly a possibility.