I don't see any problem with the fixing process. Fix is done to the completion of the process. It is true that T-MAX and Delta films require longer fixing time to fully eliminate undeveloped silver salts, but fixing bath is not the best way to wash out the dyes.(posted 8480 days ago)Some may worry about overfixing may dissolve image-forming metallic silver. However, as long as you use an alkaline or very weakly acidic fixer like TF-3, TF-4 or Ilford Multigrade Fixer (anything that has hardner or says you can add hardner is not in this category), soaking the film in the fixer for 20 minutes or perhaps longer won't be any problem, as long as the fixer usage is within its normal capacity.
I don't care much about the dye in TMX but soaking the film in plain water for 20 minutes or in fixer remover (sodium sulfite 2% solution will do) for a couple of minutes should take care of it.