I have 2 legend dwellers and both are at 30% happiness and won't raise higher. They arnt hurt. I've put them in live quarters with girls and both have made 2 babies. I put them to work with there special traits in mind and now have them working out and nothing has helped. They were 100% before I completed the full bottle and cappy quest. One of them has said they are tired and want rest but idk how to make that happen. Idk how to raise there happiness. I've tryed everything I can thing of.
The four reasons that a dweller would be unhappy are:
- Injury: Try healing the dweller with a stimpack and see what happens.
- Job: Make sure that they are assigned to the right job according to their SPECIAL attributes.
- Irradiated: Try using a RadAway on them and see if that fixes it.
- Hungry/Thirsty: Make sure you have enough food and water.
You can also zoom in on a dweller to see why they are unhappy. If what they say doesn't give you any clues you could try and change your radio station from recruitment to music. And if all else fails I would suggest following the previous suggestion of sending them to the wasteland and let them come back for a coffee break.
The mention of rest is usually linked to to injury or radiation. Not sure about hunger and thirst but those would be vault-wide problems.
A big source for unhappiness is working in a room with a corpse, which will be communicated by affected dwellers.
But there was (is?) a bug where rooms can be marked with an "invisible" corpse which can't be removed. The only solution I know if that happens is to delete and rebuild the room.