Well, they don't have to tell us the reason they pull them. Even being seen as "potentially" offensive would do it.
But I think Beckett437 has the right idea that it's most likely downvotes. That could mean anything. Maybe the most likely is that your memes had a political or religious view that the first few people who saw it didn't like.
It's happened to me twice that I've made memes making fun of Trump and they've been bumped back into submission almost right away. I assumed it was downvotes.