Before you do anything check this out!
If you have a blue cast to the transparencies, is the border also blue? If so, it is as stated above, a process problem (or perhaps a bad batch of film). If the border is black, but there is a blue cast to the image it is more probably an exposure problem. This could be either your error or it could be a slight deviation in the speed of the film itself and can be corrected by a yellow CC filter. It will be hard, in this latter case, to separate out a slight exposure error from a slight speed deviation of the film.
Use of a color temperature meter will help determine which of the latter it is.
Don't make changes to the solutions until you check out the border. If it is a true process problem, the blue color cast will extend into the border. In fact, blacks overall can look thin and blue.