Haven't thought about Gusttium too much yet, but yeah. Also food competitions and also people bringing food from all over the land. 

In regards to the current festival, I'm thinking it will be more like scattered decoration half set up. Wide eye people paying little to no mind to the ones trying celebrate (most everybody is traumatized from the previous day, while the ones trying to celebrate are trying to forget what happened and act like nothing was wrong. Then there's the issue with the Cult going around and taking all the food from vendors that they could find, while everyone was going crazy the previous day. Another reason why people aren't celebrating, they are panicking. 

The main idea here is, that your characters should be going into town thinking it eerie/weird how almost nobody is celebrating. That today is the most depressing Olfaccium Festival that they ever saw. The characters should understand why that is, but still eerie. I may have a story teller pop in though (one that nobody is listening too or they're standing there wide eye, half listening). Might throw in some riddled lore there.