upset bunny belly

I looked up that fly strike and none of the symptoms seem to match what is going on with my bunny. I think her stomach cant handle lettuce and greens liek that. Because I have been watching what I have been giving her and some of them like carots and green peppers are nto bothering her.

I think you may have given yourself a place to start seeking your answers.From what you said,the runny poo disappears when you stop feeding the Veggies.
You're going to have to look more closely into what type of vegetable you're feeding,and how much.
You will know if this is the case within 12 hours of feeding the offending food.If you are feeding a variety of greens, and not sure which one is causing the problem, then feed only one green food every 48 hours until the offending food is identified and then simply remove it from the diet.Make sure to rinse your veggies well with water .Wet leaves will also help the bunny take in more water as it's dealing with this problem.