My Homemade Wholewheat Sourdough Bread - Too Sour, Hard Crust

My sourdough whole wheat breads are too sour.  The lactobacili bacteria apparently really like the germ and bran and have a field day during the bulk ferment, multiplying and multiplying.   I know for a lot of people, sour is where it's at, but I like a bit of sweetness in my whole grain bread.

So I'm working on fixing it.  Adding sugar and honey hasn't helped - only made the taste sharper, it seems.  I've already been doing a cold ferment, either in the garage or in the fridge, to see if that helps things, but I think it might be at the root of the problem.  I'm hoping a shorter ferment (I've been doing two or three days) will sweeten things and solve the problem.

Crumb of Whole Wheat Sourdough

My whole wheat breads have a tough crust.  This one here is actually the most successful to date - the crumb was only semi-dense, and it had some noticeable, if not impressive, oven spring.

Whole Wheat Sourdough Loaf With Spelt Starter

Here is an example of a dismal failure of a spelt bread I attempted to make from a spelt mother dough.  It was flat, spread out, with a thick, dense crust, and very sour.

100% Spelt Sourdough Bread from Mother Dough

It did have some interesting holes in the crust that are visible in the picture.  Not sure of their origin; I suspect it may be an effect of the motherdough.

Crumb of Spelt Bread - Nice and Open

The bread had a crumb that wasn't that bad, but as I said, it tasted pretty sour.

Oddly, when I made a loaf of spelt bread last week, with three tablespoons of honey (unlike this loaf, which had no added fat or sweetener), it was more sour than this loaf.  Why is that, I wonder?