Common reason for elbow pain from swimming?

I am not an expert, but the first thought in my mind is that you are not rotating your upper body enough.  Sometimes only the hips are rolling, and you may in fact might not be rotating in the upper body sufficiently.  I would suggest having someone knowledgable taking a look at your form if possible.  It's difficult to know without actually looking at what you are doing, and what you may "feel" like you are doing might not be the case.  Hope you can get some help!

Have you suddenly increased swim volume?  or started swimming with hand paddles a lot?

Often weak forearms can cause similar feeling.  You could decrease distance a bit and add some forearm specific weight training until you build the required muscles if that is the case.

Volume is up, but leveling off for a while.  I swim about 8-10,000y every other week.  Between weeks are about  6-7000y.  I have very strong forearms, but I suppose they could be unbalanced for swimming.  I am a former golf professional.  Any specific exercises, or just a balance forearm curl and reverse curl?

Hyper-extension was my initial thought. I thought it might even be from stretching, so i laid off some of the lever-type stretches. I don't think breathing is a cause for mine.

The only other idea I have, besides what I posted earlier, was that I was somehow digging too hard, when I push off the wall, the first stroke is always on the left side. I started swapping that around, but it hasn't changed the pain. I thought that perhaps I was pulling/digging too hard and in a different position than normal, because I was in a short glide off the wall and not within my normal roll. Does that make sense?

... I'm not sure that makes sense to me and I wrote it...