Yes, cecals are the grape cluster type rabbit poop, and they are semi firm, but can be smooshed into fur if sat or stepped on. If there is an imbalance of flora in the GI, the cecals can be semi formed and more mushy, to completely unformed and very mushy. Cecals can be somewhat smelly, and the less formed they are, the more smelly they will be because of an overgrowth of bad bacteria. Here are some pictures of normal fecal and cecal poop, and also some abnormal rabbit poop.
http://www.medirabbit.com/EN/GI_diseases/drop/Drp_en.htm
I'm still not sure what amount you are feeding, but the general recommendation for adult rabbits, is 1/4-1/2 cup of rabbit pellets per 6 lbs. body weight, and unlimited grass hay. But it's very likely that too many carbs and/or protein in your rabbits diet, is the culprit. I checked out the Wagg food that you are feeding, and I can see a few problems with it that could be the cause of the poopy bum. It looks like it is a 'treat' food, and is chock full of carbs and protein. Peas generally shouldn't be fed to rabbits. Whole corn should
never be fed to rabbits, as they have too many quick carbs, can contain dangerous mycotoxins, and whole kernals can cause GI obstructions and create a deadly blockage. It also contains lots of other grains as the first ingredients in the food. Grains should always be a very minimal amount in rabbit food. This food would be providing far too many carbs for your rabbit. Too many sugars and carbs can actually lead to dangerous digestive issues, aside from a poopy bum. If not corrected, it can lead to a potentially fatal GI blockage called GI stasis. A poopy bum is just the start, and the gut imbalance can continue until you are dealing with a blockage. I lost a rabbit to this exact thing. I'm not sure what your adult rabbit food is, but a plain rabbit food without treat pieces, is the best thing to be feeding rabbits. Timothy grass based pellets are best for adults, but a lot of people will feed lucerne based pellets. But you will want to limit the pellets based on your rabbits weight, but you may have to adjust up or down on the recommended amount, to keep your rabbit at a healthy weight. In addition, feed unlimited grass hay, and veggies are good as well.
I would suggest to stop feeding the Wagg Bunny Brunch, right away, and that may solve your problem. If your adult rabbit food, has treat pieces as well, then you will want to gradually transition off of that food too. But I would stop the Wagg food first and give it a few days to see if his poop goes back to normal, and doesn't have mushy poop or excess cecals anymore. If you need to switch to a plain adult rabbit food as well, then you want to do the change very gradually starting with a small amount of the new food added, with a similar amount of the old food decreased, and slowly increase new food/decrease old food, each day, until at the end of 2 weeks you have completed transitioning to the new pellets. Keep an eye on the poop, and as long as the poop doesn't get mushy, and stays normal, then your rabbit is doing ok with the transition. You do this kind of thing with any new food you introduce to your rabbit, like pellets, veggies, but you don't need to with grass hay(non grain grass hays). Doing this gradual introduction of new foods helps give your rabbits gut flora the time it needs to gradually adjust to the new food. I'm including some good veggie lists for rabbits too, and how to introduce them to your rabbits. I would wait til your rabbit no longer has soft poops, for at least a week, before you try to introduce any new veggies to him.
http://www.3bunnies.org/feeding.htm#top
http://www.rabbit.org/care/veggies.html
