Well technically one shouldn't have turkeys with chickens. /looks askance So be glad!
On the ones in the woods - did they get black spots last year? Weird thing here - we usually have pox, little cases yearly. This year - birds not on old ground, not on ground at all, hardly any mosquitoes (we were in a drought), and the worst pox yet. Go figure! But surely your mosquitoes this year started something. Who knows what they do when we're not watching.
It can be other insect vectors, but honestly I can't imagine what could be more infective than mosquitos as far as bugs go. So if yours didn't have pox last year, it could be they just missed it.
Mine - and I almost hate to admit this - but the ones that had pox this year I didn't separate out. I figure everyone in the cage at that point was exposed. Most all got a spot or two, two got none, several got quite a few, the turkeys got hammered. (First case of turkey pox ever...) So honestly as far as the new roo with the old flock, I wouldn't worry horribly.
It's the younger ones I worry about more - because they're just more delicate. But my younger ones have always done good, so hopefully yours will too. Maybe they'll not get it at all. I wonder if they were vaccinated?
The diphtheric cases are just the ones that worry me. Honestly I never worried about combinations until this year when I heard of two. Most of the literature says only one or the other. But my disease books say both is possible, and low and behold... But hopefully it's not common.
And yes - most literature - even great disease texts say "no treatment" - but good old practical poultry keeping, there are some treatments to prevent secondary problems. So technically and correctly there are no treatments for the virus pox. So sometimes the wording of those books and the technical papers is misleading to people like you and me who just want our birds to be healthy first, technicality of rules come second.
That was another important lesson I learned this year: Everything you know about pox, rethink.
P-Rock might be fine. Honestly a bad case often turns out fine. (Boy, haven't I learned that this year - seriously I could kick myself for not photographing the turkeys - I just have 2 cockerels.) So if you keep her - or not - keep that in mind.
Hopefully your cases will be done soon. Seriously it was the last minute when mine dropped scabs. It was day 1293 = scabs. Day 1294 = brown scabs. Day 1295 = disease? What disease?
<--- For those reading this, I'm joking about it being 1295 days - just felt that way.
HUGS to you. it's all a learning experience even after years of it. There's always some good new yucky surprise for poultry lovers!