I have not found different manufactures caused any big differences, how much metformin are you on at the moment? If not on the max it might need tweaking the dosage but see your doctor or DN to see if this needs doing.
If you are on the max like me and your BS is rising you might need to have additional meds to help bring your levels down.
What readings are you getting? your doctor may well as for a new HbA1c test so they can compare them to your last results. I recently had 3 HbA1c tests done over a couple of months which showed my BS rising and eventually gliclazide was added to the cocktail of meds.