First Eggs and Diarrhea Common?

We have 5 chickens who are 24 weeks old. They were vaccinated as day old chicks before they were shipped. We live in Denver. One of the 5 started laying Jan 2 and has laid 6 eggs since then! Yesterday and today she seems to have diarrhea. I've been reading and looking at pictures and I can't tell between the looks of Clostridium perfrigens or general diarrhea. Our chickens live in very clean area, mostly because it's new. Would she be old enough to get Clostridium perfringens? I've read all kinds of things can cause diarrhea (stress, heat, sudden cold etc...) but she seems to be the only one who has it. She's eating and acting normal. She's the "alpha" hen, a Golden Buff (Comet). I haven't read anything stating that starting to lay eggs can cause stress (and diarrhea) but I've wondered if that could be it? It would make the most sense since she's the only chicken of 8 (the other 3 are 21 wks) that is having this problem. We did have sudden cold and more snow a couple of days ago, but again, none of the other chickens are having diarrhea. Any thoughts?

They were likely vaccinated against Marek's so that has nothing to do with the current circumstance.
Clostridia is common and no way to tell why some get a bigger bloom than others.
I thought some of my chickens had a roundworm infestation. A fecal sample showed they had no worms but a bad clostridial infection. Tetracycline cleared it up but I had to throw eggs away for over a month.
There is also no way to tell what is going on without having a fecal sample read. Don't guess or ask others to guess, get lab work.
Any vet SHOULD be able to do it. Whether they will depends on the vet.
Here's your state poultry lab. They will do it.

Colorado State University Veterinary Diagnostic Laboratory-Rocky Ford
27847 County Road 21
Rocky Ford, Colorado 81067
Phone: 719-254-6382 Fax 719-254-6055

Thank you ChickenCanoe. Our dogs' vet has an Avian specialist, so I can take a sample there. Is it possible that she laid two eggs today? She definitely laid one this AM, but another showed up late morning.... We have one other chicken who lays the same color, but none of our other chickens have been acting (squatting) like they are ready to lay.

Not 2 eggs in the same morning. Ovulation usually doesn't happen for at least an hour after the previous egg is laid and it takes about 25 hours to build an egg.
You have another layer. Not all chickens will squat and it is more a sign of the desire to breed than whether or not ovulation is imminent.

Alright. It must be our New Hampshire Red then! Didn't know that! Yay! Thank You for the information.

Yeah, the shell gland is very small and 2 eggs can't occupy that space. The egg spends about 18 hours there getting the shell built and pigment applied.