Wheezing and boogers!

My grandma took in some babies and two feral fixed moms from her brothers barn. The two babies but especially the little girl coughs and like wheezes sometimes. She sneezes a lot too. We're trying to get them an appointment but the vet is all booked up right now. We're wondering what t might be and if there's anything we can do now to help her out.
This is Baby the girl.

And her crazy brother, Spitfire

And this is one of the fixed feral mommas. We think she's Baby's mom.

Impossible to diagnose her via the internet, and particularly since we aren't Vets, but it could be allergies, could be an Upper Respiratory infection, could be asthma, could be a cold, could be Feline Herpes, could be something else. 

Is she eating well?  As long as she is eating and drinking well, she can probably wait until you can get her in to see the Vet, but if that changes,then she may need a quicker intervention.  If she gets too congested, you can try warming some stinky wet food to see if that helps, and you can also try putting her in a steamy bathroom to see if that helps. 

She's been eating like a horse. And I told my grandma to do the steamy bathroom trick to help if she needed it. No other cats have any of the symptoms she does either. So I was thinking possibly allergies. Some days are worse than others too.