My granddaughter had somewhat the same experience, with one breast suddenly not allowing as much milk to come out as the other side when pumping. It wasn't getting "all" the milk, as the other side was. Within several days, production went down, despite massage and further pumping on that side each time. 

I told her to try some larger flanges, but several lactnetters suggested trying various smaller flange sizes on the breast that was not removing as much milk as before. That did the trick, and allowed removal of the "full" amount of what was in the breast with each pumping. However, within a few days, production had started to go down, so I had her do short (10-15 minute max) pumpings more often on that side during her waking hours for a few days and the increased frequency on that side brought the production back up. 

She also had an area that had been somewhat tender and swollen during pregnancy with the OB saying it was probably a "cyst". This began to bother her even more, so we decided it was worth taking lecithin at regular intervals round the clock, along with massage of the uncomfortable places, to clear up the sites that felt like they were threatening to have blocked ducts. Things have been normal since these interventions were done.

These suggestions may or may not work, but certainly won't do any harm.

Best wishes to her.

K. Jean Cotterman RNC-E, IBCLC
WIC Volunteer LC      Dayton OH

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