How do I make this tank more likely to succeed - 3 bettas?

Hi everyone! I have a 10 gallon tank (going on 5 weeks now) with 3 female bettas in it. They are doing pretty well - bright colors, active, hungry, exploring the tank, etc... There is a definite hierarchy (Ruby>Daphne>Scarlett) with some posturing, but not too much chasing, and I haven't seen anything serious in a few weeks. Scarlett got nipped while I was away on vacation two weeks ago, and it is healing up. All in all, I am happy with it, BUT...

Almost everything I hear is that 3 bettas in a tank is a recipe for disaster. Is there anything I can do, oh Fantastic Betta Experts, to make this a better situation for my girls (without getting a new tank)?

I have dividers in case I need them, but they seem to really enjoy swimming around the whole tank, so I'd rather not divide them while they're getting along. I hear that 4 or 5 bettas would be better than 3, but that they should all be added at once. (I had 4 originally, but one was never healthy, got picked on, and even though I removed her quickly, she never recovered.) Does anyone know if adding two more (quarantining first, removing mine, rearranging decor, etc...) would be a good idea or disastrous? Or is there anything else that you can think of that would help these three coexist?

Thanks!

I think it's fairly well planted. (If I posted the pic right, you can see it.) I'm nervous that if I only add one more, that one will get ganged up on. With two new ones it would spread out the aggression, or not? Eh, I don't know. It'll be a few more weeks before I do anything, if I do anything. If the best thing is to leave them alone, I'll leave them alone.

Thanks for the feedback! I'm thinking it's best to just leave them be, then. They're the first fish I've ever had, and I'd rather not mess it up if I can avoid it. Such cool little fish - I didn't expect them to have such individual personalities. BTW, in the picture that's Scarlett up top and Ruby below; Daphne is smaller and not in the pic. Thanks again!

That's good to know, WandaA. Daphne was a little bully for the first few weeks (she's only half the size of the other two!) but she's calmed down now. But I know that if I try adding anyone new that I'll definitely need a backup tank - I've seen her in action, so I know the risks. :/

It's good to know that it can be done, though. Thanks!

This is not a great pic of them, but you can see how much smaller Daphne (on left) is to Ruby (next to her). Scarlett (below) is the same size as Ruby.