So I have been on a juice fast/detox for 4 days now, consuming only about 300 calories of juice per day, and lots of water. I haven't had any of the nasty detox symptoms people have described...No headaches, no nausea, nothing at all. I've actually felt really good and not even been that hungry.
I've also been drinking cayenne pepper tea with lemon twice a day throughout the fast, and tonight I did a salt water flush, and it worked well, but was entirely liquid. I'm not sure if that's normal.

Everyone else I know who's done a juice fast like this felt really ill and tired after the first day, and experienced at least some detox symptoms, and also passed a lot of ungodly things after the salt water flush. (Yeah, sorry for that.)

I'm 20 years old, vegan, healthy weight, I exercise moderately, I rarely eat junkfood, no drugs, I don't drink often, so there's really no major source of toxins I guess, but I was expecting to get some noticeable results from the detox at least.

So based on this information, would you say I'm doing something wrong, or should I just be satisfied with how easy my fast has been so far?

I would say that it sounds like you are doing everything right.... how long do you plan on fasting?