At this point, I think one of three things has happen:
1. Ralph/Dick DMs about a fake ID for Faith
2. Faith offered an underage nude, and Ralph knowingly accepted.
3. Ralph gave Faith some sleepy pills in LA, she somehow knows, and they talked about in DMs.
Personally, at this point, I go with 2, 1, then 3. 3 I think is the most outlandish, but somehow possible.
I don't think it's about the fake ID because Vickers tweeted about long long (days?) before he mentioned going through the Discord DMs.
I've theorized before that #2 is a very real possibility, and not only that he accepted but that he requested it.
It's not a stretch to think Faith had those pictures saved on her phone from when she sent them to Chris.
I think #3 is unlikely as well because Vickers reaction was so strong that it would seemed it's something very conclusive evidence of breaking the law. No idea how much trouble he would be in because they talked about doing drugs together through DMs.
He tweeted about going through the logs and about 37 minutes later tweeted that Ralph had 48 hours. It makes sense he would start reading from the first message, so it seems it's not that they were communicating when she was underage, especially since the first tweet was akin to "I started reading these, I should have gotten a beer for this". and he would have noticed the dates immediately.
I could be wrong though, and he saw it and spent the time between tweets talking to his lawyer (he mentioned it somewhere, I think the response to Faith's statement).
Also, I'd forgotten about how Mrs. Vickers reacted that night, she probably saw something that made her react that way, it could have been anything but I think that they were probably prepared to find the kind of things that have been discussed before (grooming since she was underage, she knew about Faith drinking, etc.), so it's either something unexpected (blackmail of some kind? Ralph does love to blackmail people) or some kind of image that shocked them.
Point is, based on the reactions (and the fact that the fake ID thing had been mentioned earlier and Vickers didn't see it as big win against Ralph/Dax), as well as how Ralph reacted during that night's show (and deleted accounts plus who knows what else) it would have to be something serious that Ralph knew was out there and was hoping Vickers wouldn't get access to it.
Either way it'll probably take time, but I do think that Vickers being confident enough to go quiet and wait is a good sign.
In any case, Ralph is fucked because if for whatever reason the cops don't do anything Vickers would then eventually drop whatever he found and that seems to be what Ralph was scared of.