Turns out I was partially wrong about Cherry. Both of her parents were "lost" during a Pest attack when she was child. Her daddy issues are very much a thing though.

Now for the actual lore bits I've picked up:
Sakura and Mei Plumblossom are close friends. They are also considered in-universe to be the strongest Flower Knights at Blossom Hill although Sakura believes that Mei is stronger than her.
According to Leucocoryne's H-scene, the Knight Captain actually is out there fighting pests, we just don't get to see it.
While my understanding of Japanese is extremely limited, I didn't need to understand Japanese to get this part. According to Chapter 2 of the Flower Knight Girl prequel manga, Alstroe Maria was heavily injured trying to protect a rabbit from a pest before she became a Flower Knight.

While not really lore I thought these were neat little facts:
Mei Plumblossom has yellow/gold coloured eyes.
We all know that Convallaria is a yandere. Specifically an eliminator yandere (she gets hostile if others get near the Knight Commander). But did you know that it has heavy ties to her flower? All parts of the Lily of the Valley (a.k.a. Convallaria majalis) is poisonous to prevent other animals from eating it's seeds.