Hi! From what I have read on here, it is best to ask the head of the clinical committee for a status update rather than the individual POI If you are uncertain, you can call the Psych Department office and ask them who you should e-mail. I only applied to a couple schools so have limited experience, but I was in contact with the psych office and they told me I was on the waiting list and gave me the name of who I should e-mail for further info. It's a smaller program though so not sure how others work.
As for asking about improvements, I am not confident that I can give the right advice but hopefully someone else can help. I have just heard it can be risky to ask the POI regarding status updates/potential improvements but it likely depends on the individual!