Have Cat Questions? Ask a Cat Vet Online.
I am sorry to hear you are worried about your cats. My name is Rebecca. I am a veterinarian and will do my best to help.
How were the colds treated: antiviral medications, antibiotics, fever medication? Or let nature take its course?
If this was a viral infection like a cold, it can take 10 to 14 days to get well, so maybe they just need a little more time. For the one that is growling, I would take her temperature and see if it is normal (101 to 102), and if it is still high (over 103) an anti inflammatory/ fever reducing medication might help. If she is still sneezing at all, you could try children's nose drops, 1 drop once to twice daily, such as Little Noses.
If you look at her gums are they pink in color, or pale?
L Lysine, an amino acid, might help if this is a Herpes viral infection.
How are your cats doing? Can I help with or answer anything else? I hope you were able to see what I wrote.