As it stands, sentence A means nothing. Sentences B and C use "good shape" and "bad shape" correctly. As Rover said, it's "these days", not "in these days".
Well, if your trees have recently been exercising and staying fit, then I suppose it has meaning. Maybe my trees are just lazy, but they mostly just stand around growing fatter and older. Occasionally they wave about a bit in the breeze, and on rare occasion fall completely over. Otherwise, they stay rooted to one spot.
I can't help but envision Ents wearing jogging headbands, although that does seem a bit hasty for an Ent.