Image tone is determined not only by the developer but by the paper. It is impossible to make a developer that will produce the same tone with all papers.
You can change the tone a bit by adding either potassium bromide or benzotrriazole to the developer. Bromide will make it warmer and benzotriazole will make it colder. Try adding small amounts of a 10% solution of KBr or a 1% solution of benzotriazole. Start with 2.5 ml per liter of working developer.