guinea pig droppings

Question
My guinea appears to be in good health and has been to the vet for this problem, no real answer there.
About a year ago some of her droppings changed from  a normal shape to a large mass of droppings stuck together. The vet thought she might be constipated and suggested a diet change. But she's a picky eater and so she lost weight. The dropping problem still exists.
Thank you for helping me.

Answer
Eira,

I am sorry that I am just now getting back to you.

It could be caused from not enough water, and not eating enough hay and grass. Start giving her water every two hour for a week or so from a dropper and then make sure your getting the same type and brand of food continually. That way she is more likely to eat more. Also set her out on the grass (untreated, no weed killers and fertilizers) for about 30 minutes each day and see if that doesn't help get her poop back to a more normal deal. Other then that there isn't any other reason for the issue.

I hope this helps,
   Take care,
      Jules