I suspected its the scanner. If you say the rolls is in a wrong way, ur outcome will be reddish if you use C41 rolls so called 'red-scaling'. If you use E6 rolls and accidentally cross-process C41 it will turnout blueish and a bit look underexposed.
what does "red-scaling" means. When compared with "normal" film negatives, my film does look "red" under the scanner light, instead of the more "brownish".
My expired film 2004 also turns out like this. Maybe the sensitivity is wearing hence result in under exposure....when I use a new film everything was normal.