To give you an idea of where this is going, ultimately, look around at social media and you'll see photographs that you may recognize from photographers being used as posters, memes, etc, shared and re-edited, over and over. They're not even images that someone who edited it paid for or were even a part of. They just took it straight form where ever they saw it, edited, added, etc, and it just gets shared and moved around the social network block for years. Nothing they can do about it really either. Not worth the cost to truly "take it down."
When it comes to social media, in general, I would suggest you consider it like this... even bad publicity (reposting edits of photos you took that you don't like) is probably good publicity (in terms of keeping clients and/or getting new clients from these platforms). I would just let it go. Keep it in the contract, sure. That way if there was something serious, you'd have a legal leg to stand on. But for the common re-re-re-re-re-edit-share of everything that goes through the social media neighborhood, I'd just consider it a hybrid form of advertising and keep shooting on and not lose sleep over it. You're not losing credibility as a photographer because some kid applied a filter to a photo of themselves. And the other kids looking at their photos on that social platform, are not inspecting the work for a watermark or artist stamp. They gave it a 0.5 second look, and swiped to the next.
Social media is a fight I'd stay away from.
I'm in the camp of, you got paid to provide a product, you provided it, everyone's happy, don't worry about what they do with it later unless it was used commercially and you found out about it (that's where your contract comes in handy).