If your parameters are fine, then you should be ok to add more.
Beware of aggression from the labouti toward the flame. Use a social acclimation box to introduce new wrasses to existing ones.
Do not get a pr of flame wrasses, especially for a tank that small. Wrasses don't form bonded prs, rather, gender is determined by social interactions, essentially the male chasing and displaying to the female, which can be srressful to the female in a small tank. Also, females often transition into males in aquaria, even if a male is present. If that happens, there ends up being a lot of aggression between the males, that leads to one being forced into hiding, oftentimes death.