I've never had a sorority, so this is all based on info I've read online.
For sororities, whether they've been up for months or not, fighting will mostly likely occur. And yours is "only" up for a month (a month really isn't that long, actually). Like a "ticking time bomb" I think I've read before. If it's not working out, you may have to take some of them out into their own tanks. Or if you're willing, keep them in there? I wouldn't recommend it, but I'd wait until someone who has experience with a sorority came on that . And are you sure about the plants? Did you run a pantyhose across it? The slightest snagging/tearing indicates it may rip your bettas fin.
I think they're still fighting, though. Just because you didn't see it doesn't really mean much, the evidence is somewhat there. It's like a tailbiter - it's tailbiting, but you never see it. Or rather, you hardly see it. Hopefully none of the girls gets hurt too much. Good luck!