Oh iceburg lettuce just sucks for most critters including humans (rats get the runs from it too). Mostly water really and little else. I don't know if you already do this Sheree but back when we had pet rabbits I used to have a nice deal going with my local friendly green grocer. As long as I arrived at a certain day and time I could have a literal ton of lovely free veggie cullings for the buns. I did have to pick and choose a bit to get the best but most of it was actually quite good. Just things like misshappen carrots, etc. but a lovely free supply of extra munchies for the bunnies.