Small Poops, Small Food Intake

Ive had Tundra my dutch cross for a week now! Shes been settling in well! Loves to cuddle and explore. However I noticed most of yesterday morning her poops were smaller then normal (About half the size) and she hadn't urinated all night. She also refused the food I had out for her. So i quickly changed her litter, offered fresh veggies (Lettuce, thyme, cucumber and a bit of apple), changed her water and pellets. She seemed uninterested for a while but the fresh hay was finally eaten a bit and by afternoon her poop was normal and she had urinated. Is this something I should be concerned with? Im a first time bunny owner and I just want to make sure Tundra is healthy and well.

I have read that cucumber can cause digestive issues. And you want to limit how much apple or other fruits you give. As a first time bunny owner, you might check out the list of approved foods here: http://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
Small poops can be a sign of the beginning of GI stasis, so keep an eye on that. I have less experience with the urination issue. How you are giving her water? Is it in a bowl or a bottle? Make sure if it is a bottle, that it's working, and if it's a bowl and they have never used one, you might consider switching to a bottle. Is she molting? I would push the hay when that happens, and also maybe just give some romaine lettuce because they will get water from that too. It's kind of hard to say, because it could be a lot of different reasons, but these are some of the things that come to mind.

This is a good explanation of GI Stasis and a really good read. Hope it helps: http://www.rabbitsonline.net/showthread.php?t=23808

Also, its good to make sure you have syringes, small ones, incase you ever need to syringe fluids/electrolytes, because if your rabbit ever does get stasis you will probably need them to hydrate your rabbit.