Just to clarify, these are not the ceceotropes? Right? the ones they are supposed to eat? Is it just a big sludgy smelly gob? If so, then it can mean a few things – 1. The overgrowth in bacteria you talking about. 2. The bunny is overweight 3. Stress 4. An underlying health issue.
If it’s due to diet, then sometimes it can take time for it to get better, even when you change to a better diet.
Here are some guidelines on what your bunny should be getting. http://rabbit.org/faq/sections/diet.html Be sure to pay attention to the section where it shows what should be fed at what ages.
You can also see what helped in Bailey’s case on the diet page of this site (Note: Bailey now gets poopy butt only because of her spine, and the weakness in her back legs due to e.cuniculi – she can’t clean herself completely.)
Regarding Petromalt: I have heard both sides when it comes to petromalt/laxatone, but I know that SaveABunny has used it and I have as well, WITH the caution in mind, noting that if it did not help or improve things rather quickly that medical care would be needed asap for continued GI stasis.