2013 return was due 4-15-2014 and the statute of limitations is 4-15-2017, three years from due date, so you cannot amend the 2013 return.
2014 will expire 4-15-2018.
Only amend the return's where there is it impacts refunds or taxes due.
IL does have an educational credit so you will need to look at those returns also.
https://ttlc.intuit.com/replies/3288565