Can we see a picture that shows the fan blowing on plant A and B? I'm more inclined to think that your issue with your plants is in the root zone and the air itself blowing on the plants isn't really contributing that much to the way they look.
To better assist you, please list in as much detail as possible the grow media you're using including the size pot; your watering frequency and how much water you're using; and any nutrients or amendments you've been using. Also please list your daytime temps and RH readings as well as temps and RH when your lights are off.