Let's see.... Panel1: need a comma between hallucinating and or, "Am I hallucinating, or did your style just change?"
Twilight's speech: Revise Structure. The entire structure of the sentence is a little out of whack. Possible alternatives: "Heh, this is just like following someone when they're improving their drawing skills!" "Heh, this is just like following someone when he's improving his drawing skills!" um... you really need an object after 'following' so we know WHAT the're following. Also, "He's" means: "He is", because it's abbreviated, or made shorter. You want "His" which means that the skills are his, or that they belong to him. You could also use they're/their to be gender-neutral. (don't know if boy/girl)
Rainbow Dash's speech: First two sentences are good. You used the right he's/his. "How silly idea!" isn't quite correct, "idea" is a noun, must have a particle. ("The" or "a") I also don't think "How" is the right word to use either. How is usually used to indicated a question of method. ("How did he do that?") I would use this: "Such a silly idea!", or if you REALLY want to use "how" you could do this: "How silly of an idea is that?", but that's a bit big.
Once again, don't get disheartened, you learn the most when you make mistakes, so think about how much you're learning! Keep up the good work, keep deviating!