So to update.
The marans pullet who was quite gurgly, sneezy and wheezy made a full recovery with garlic, oregano oil and vitamins in water as well as cinnamon in feed. That’s all I was able to offer quickly and after a week she was back to normal. She’s even squatting now and will be laying soon!
The littlest Orpington pullet had same treatment and also recovered from the gurgly throat.
The splash ameraucana with sour crop recovered but I’m less sure of what exactly helped. I tried everything for her and nothing seemed to clear the gooey mass in her crop. I ended up having to treat her for lice and used Ivermectin which I think inadvertently dewormed her also as I found a worm dead in her poop following. After nearly 2 weeks of having her quarantined I had to go away and had to put her back with the larger group. She seemed to make a full recovery after that!
I still don’t know exactly what her issue was or what killed my Barnevelder pullet. In all of that the splash stopped laying, but her comb is reddening again so likely to start again soon. I just thought I’d update in case anyone has similar experience in the future. I now have VetRx on hand for future...