John:

Watch yourself say these lines in a mirror or google "phoneme mouth charts" or something like that. Your lip sync needs some work. It looks like he is just moving his jaw up and down. I do see some variation in the corners of the mouth, which is good, but I feel like you could benefit from a little more research.

Timothy Muller:

Hi there! My biggest advice for you is to advance your facial expressions. Your short especially has close ups that relies heavily on strong facial posing. Try recording yourself or find reference of facial expressions and match it as closely as possible.
Keep up the good work.

Riley Thompson:

watch your moth shapes, i don't know if its a rig restriction but they all the poses look really stiff in the face