Would not worry about the slight coloration difference as long as overall health is fine. They are two different varieties in the pic and two different locations. One may have better uptake of nitrogen, ph could be different. A good fert to try on yellowing leaves I find the Fish fertlizer 5-1-1 works great for me, I also have used MG but find the fish to have better results.

Sometimes no matter what you add or try to change it stays the same, a previous post had the same issue for the whole season, the plant produced fine but stayed a yellow green.

ph imbalance to much water or fertilizer. mine are in raised beds. same peppers but are only watered when the leaves are wilting. be concerned if they start getting yellower then start thinking of backing off on the water. its 107 here today and i only water once a day that is when they start wilting. they are very dark green.
hopes this helps

My soil is very loose and fluffy. Drains very fast..I don't want to underwater.

Let the plant tell you when it's thirsty. Getting good and wilty won't hurt them, and encourages root growth.

I watered with soaker hose last night at 5pm.
Then came in with the watering can and gave them avoid extra soaking.
It was about 80.
Today was 90 all day and 1/2-1 inch under the soil is still moist.
in this case I wont water till tomorrow morning.
Does this seem about right?

And gave* them a extra soaking