For the Serpent and Centaur constellations, you could give bonuses to stealth/archery skills instead of "the character can use X." Then, these bonuses could still be spent on stealth or archery while moving, but there would also be other bonuses, so overall, the constellations would become more symmetrical with the Warrior constellation.
The Rabbit's problem is probably that we're talking about a group. Therefore, this ability only makes sense for solo actions, primarily for assassins. Or for non-combat characters (but it's more beneficial for them to take the Craftsman). Therefore, to make people take the Rabbit, there should be a bonus for scouts or craftsmen. Maybe something like "potions are X% more effective on the character," I don't know what else, so as not to repeat.
Crown – I didn't find any skill that would give the same effect. There are, however, more complete immunities, but they are quite rare. And there are active skills, like Sprint, which Siv took. The question with active skills is, let's say Siv was the Crown. If he used Sprint, would he get the stats described in the Crown constellation, or not?
My suggestion is to change "or" to "and" for the Crown. Let there be stats in any case. If it's too strong, weaken them a little, but let them be there.
Of the monthly constellations, I would weaken the Hydra a bit; it's a no-brainer option for a pure combat character. Not only do you put unnecessary stats into the negative, but the percentage bonuses are also too high.
Wolf – I would give it a little more critical hit chance.