You have described two different off-flavors/aromas: sour, and rubbery.
Sour is likely from some bacterial or wild yeast contamination. Can you describe the sour flavor? Is it like vinegar, or like sour milk? Vinegar character is likely from acetobacter. Sour milk character is likely from lactobacillus. The most likely time this may have been introduced is during transfer of the yeast from one batch to the next. How did you transfer it? The safest method is cone to cone transfer. Dump the bottom sediment in your conical until it turns from brown to light tan/cream color. Shut off the valve, and change hoses, Make sure the hoses you hook up are as sanitary as you can possibly get them.
Now connect a hose from the primary to your next fermenter (empty). Make sure you have a sight glass inline so you can observe the yeast during transfer. Open that valve one the empty (sanitary) conical first, then open the valve on the (full) primary from your last batch. Watch the sight glass and close the valve when yeast slurry becomes beer. Now transfer your cooled wort onto the yeast in the empty fermenter.
With proper sanitation, you can dump the clean yeast into a sanitary bucket and put a lid on it and keep in it the cooler for a day or so.
This gets to your second off aroma: rubbery. This is likely from yeast autolysis. Basically, your yeasts have gone cannibal and begun consuming the dead cells in the culture. Hefe yeast is extremely fragile and short lived. So much so that i understand most German breweries that bottle condition use a lager yeast in the bottle for their Heffeweizens. I do not brew much heffe, but I have been told be many that this yeast will not last more than a day or two between batches unless you take extra measures to keep it viable.
Unfortunately, I don't think there is any way to remove these off characters from the beer you have, you just have to learn an move on.