You may want to make sure your early payments are going towards paying down the principal, and NOT pre-paying future payments/interest. I have heard Dave Ramsey mention this several times to callers regarding student loans, so even though I never personally ran into it, it must be a "thing" that commonly happens if you don't specify & verify that you want the early payment to go towards the principal. He acted like it happens to a lot of people, and that you may have to be persistent with some student lenders to actually speak to someone who understands what you are requesting.
Yeah, it looks like they have applied all your 40K in payoffs to future payments instead of principal. if you do the math on balances of:1,481.07 @ 0.042519,845.7 @ 0.051644,893.53 @ 0.059618,049.23 @ 0.0559you'll get $13.07 in interest daily.