For starters you might want to try changing the developer. A warm tone developer might just be the thing, since it should have a very subtle effect. As an alternative to a purpose made warm tone developer, some plain vanilla MQ developers using potassium bromide as a restrainer like Dektol can be made to behave like a warm tone developer. Add some extra water, 1+4 instead of the usual 1+2, run a few prints through, bottle it up and use it again the next day or two later. Activity is lower, and paper speed is somewhat diminished as you'd expect. I've tried this trick with Bromophen, a PQ developer with benzotriazole as the restrainer, and it doesn't work. I'm not sure if it's because Bromophen uses phenidone instead of metol and/or bezotriazole instead of potassium bromide.
Ilford's multigrade developer uses dimezone-s and hydroquinone as developing agents with potassium bromide as the restrainer. It might work.