I think the blue colour is a anti-halo dye, which is usually removed by fixing. Using Ilfords Hypam, I get this effect, when using more than 5 T-max/Delta films per 500 ml diluted fixer (1:4).(posted 9104 days ago)So your fixer is not strong enough (anymore)or fixing time to short. Hypam requires 3-5 mins for T-max. The T-max films seem to be harder to fix than Tri-X, Agfa, Fuji etc.
You'll find plenty of good information on kodak fixers on their web site. As I'm not sure that a handful of crystals per litre is a proper concentration.
We are using Hypam, because we used to use Hypam 10 years ago and never had any trouble, as long as it was not too exhausted. A 5 liter tank costs about 20 Euro plus tax.