Not repeating the above, all i am adding is do not worry about it too much, yea the flower gem reward is nice, but move on to higher maps, untill the maps are too hard and then go back for them.
On the event/time limited maps you might struggle to get them three stared, but most of the time this forum has some one who can help you with optimum starting position, and no event so far requires you to three star them for event rewards, they used to but changed it some time ago.
And making sure, you know you can move the groups stating position so they can start from different Tents?