May I (a person from Chemistry ) dare make a suggestion for your kind consideration?
While depositing Mn from MnSO4, one finds TREE FORMATION(in some cases) in the deposit which decrease the current density despite maintaining the required conditions necessary for Mn deposition.The paper with the followng reference has discussed this auspect:
Hydrometallurgy 84 (2006) 204–210.
No doubt, Cu and Mn differ largely in their electropositive natue[Cu^2/Cu=+0.34V and Mn^2/Mn= -1.18V ),yet I feel that it is worth trying the same precautions to avod the FLOWER FORMATION in Cu.