Heat stroke or Mareks?

I hope someone might be able to give me some advice...

I have a light sussex, approx 4 months old, which I'm assuming had heatstroke. It was 30 Celcius today (summer here in NZ) and I found her unable to walk (stumbling a few steps max) though still fairly alert. I could pick her up whereas she's not normally a fan of being petted. She didn't have splayed out wings like I would have expected from heat but maybe she didn't have the energy to do that?

Her pupils are really weird, they're going from tiny to huge constantly. Like in, out, in, out.

I've got her inside in the air con but she won't drink and is panting very rapidly.

She did have a tiny bit of banana soaked in water but otherwise is just sitting there panting.

I introduced her and 2 sisters to my flock 2 months ago - from a very reputable breeder and a 6 week quarantine - but I'm terrified of an illness spreading.

I'm treating it as though she has heatstroke....but how would I know if it was Marek disease? It seems like the symptoms are quite similar.

And how long would I keep her inside for ( assuming she starts standing/drinking/eating ) before she can go back out with her friends?

Thanks in advance!!

If you set her down on the ground does she keep her balance? Is her head tilting to one side or the other? Is she trying to focus on objects with a cocked head? When she had the banana, did she go for it and get it first try?

Thanks for replying so fast!

When I stand her up she leans to the left and stretches her wing out to sort of prop herself up a bit before she sits back down. Was up for about 15 seconds.
When she was in the run earlier her walk was weird, sort of like she was limping (I think it was her left side then too) but again, she could only really stumble along for a few steps.

Her body feels cool on the top but underneath she's still very warm

She's holding her head up ok and moving it around, not leaning to one side.

Her aim for the banana was good and quick. I was shocked that she wouldn't drink and looked (forgive the description) half-dead yet could snap at a piece of banana.
I've given her a couple more tiny pieces which she's eaten but afterwards she pants again and won't eat.

I figure I keep getting her to take little bits of banana when she will because any sustenance is better than none?

Hm, i would think with Mereks they are always un balanced? I would see if you can use a dropper with some electrolytes. I always start there!

Thanks, I'll give it a try