Thanks for the input. It's hard to see in the pics but I don't think the polyp structure on the circular ones can be any type of favia. They certainly look structurally like a stylo, but I'm admittedly not great at coral ID -- especially on something this small. What makes me suspect the stylo (other than the polyp structure) is the fact that this particular colony has spread to other remote places in tanks before. From what I've read about stylos, the odds of it being some kind of spawning event seem incredibly remote or impossible. I haven't found any reference to this coral propagating by asexual budding but that seems a somewhat more likely answer. In my previous tank, the two new colonies that sprung up were definitely not hitchhikers since once grew on a Sea Swirl and one grew on the weir. These two colonies grew to the size of a tennis ball and golf ball, respectively and, at that size, were clearly identifiable as stylophora.
The odd thing is that, since moving the colony to its current tank, it hasn't grown much. It seems to be thriving in terms of color and polyp extension but I had my nutrients so low for so long that it wasn't growing so the emergence of these new growths in the past few months is surprising.
If anyone has had similar experience or has any insights into whether what I'm hypothesizing is even possible, I'd love to hear from you.
Thx.