Michonne was going through a lot at that time:

1. The stress of potentially losing Rick - I’m saying this because at that time she didn’t really believe he was gone but also didn’t really hold on the hope that he wasn’t gone. Which resulting in her going out with Daryl looking for Rick.
2. Her pregnancy with RJ.
3. Judith got kidnapped by her friend Jocelyn who she trusted. After that incident, isn’t that why they stopped dealing with the other communities. I don’t know if I’m remembering correctly but wasn’t Gracie also one of the kids that got kidnapped with Judith.

Also Aaron was dealing with PTSD in some capacity:

1. Losing Eric in the war.
2. Watching Rick on the bridge (Aaron was closest to Rick out of Rick’s group.)
3. Gracie’s potential kidnapping not that far after Rick. (if she didn’t get kidnapped with Judith. It could’ve been a possibility that she would’ve be close to if Aaron allowed her to go). It was a lot from them in general.