Here I am using a Kitchen Aid 6.5 qt mixer to do my recent meat sticks. One pic shows the spice, cure mixed in water, and accelerator Vitamin C, 3 tablets I think, ground and mixed in water waiting to go in last.

You can see that 7.3 lbs of meat and water doesn’t really fit too well, it climbed the paddle. The bread hook didn’t work at all, but the paddle did great. I just held a spatula horizontal and kept the meat down in the bowl as it mixed.
Actually I would say the mixing action was better with this than my 20 lb Waltons style mixer, though I do love that one. I decided a 5lb batch would be perfect for the 6.5 qt KA mixer. Also, the 16mm collagen casing from Walton’s held 7.2 lbs, I ended up using 24" of a 2nd stick, which was a pain.

The amount of cure is so small as compared to the rest of the spices it is almost impossible to get even distribution through out tour meat mix. That is where the water comes into play.

I believe this to be the case as well. Mixing the small amount of cure with some water will make it easier to get even distribution throughout the entire mix. To a slightly lesser degree, it will improve the distribution of the other dry ingredients as well.
I always put some mix water in a blender, add all the dry ingredients and mix thoroughly to dissolve the soluble stuff and suspend the rest in a slurry. Then add gradually while mixing.

to make a slurry.

A couple of books I have recommend that, but I do not since we didn’t at the meat plant I worked at years ago. I mix to the point of complete protein extraction, so the other than meat ingredients get mixed very well every time.

1. Cure#1 sodium nitrate, probably called Sure Cure by Waltons, was not mixed in thoroughly. Looks like some areas didn’t get enough cure to fix theor myoglobin color to pink.
   –solution, mix the cure1 with a bit of water first, spread it more evenly thru meat. Mix longer and more thoroughly.
2. Color weakly fixed. Didn’t use a cure accelerator like vitamin c or sodium erythorbate, whose primary use besides reducing cure time, is to fix the cure color so color degradation doesn’t happen. Waltons sells a vitamin C and citric acid accelerator they call hmm… smoked meat stabilizer or something. I don’t like it as you’re adding straight citric acid, which breaks down protein bonding and is whole reason folks use encapsulated citric acid ECA. But in any case, Marianski says primary use of accelerators commercially is good color fixing.

Just my two guesses, hope that helps? At least you say it tastes good, I just would leave whole until eating then eat quickly before color turn