Staining on Old Negatives - Dichroic Fog, Mold, other?

Hi all, have some old family negatives from the 70s. Some of them are stained - generally they appear brown/yellow when viewed through the reflective side, but the emulsion side shows silvering.

Googling around, I've come across some threads with possible answers. Based on the threads, I think the damage is either dichroic fog or mold, but would love to get a second opinion.


Questions:

-For those where we think the damage is mold/fungus, am I right that cleaning this (with one of old Kodak Film Cleaner (1, 1, 2 trichloro), Tetenal Film Cleaner or 99% isopropyl alcohol) might damage the emulsion? If so, are there any non-destructive ways to clean it?
-For those that we think are dichroic fog, I've read the dipping the negs in Farmer's Reducer then re-fixing might help. Any other opinions or stories of success?

Since these are family negatives and 'priceless' I'd like to get as sure as possible before proceeding with any sort of cleaning/repair regimen.


Negative 1 - I think it's mold given the circular/dot like nature of the damage. Note how the damage concentrated around this person's eyes, mouth and hair which are areas where the emulsion is more dense than the surrounding face.



Negatives 2 and 3 - I think the staining on Negatives 2 and 3 might be dichroic fog since the staining is more uniform and occurs in patches rather than targeted:

Probably this: https://www.filmcare.org/vd_redoxblemishes.php
Refer to this post: https://www.photrio.com/forum/threads/strange-development-storage-problem.203149/post-2744529
Thanks to @cmacd123 for pointing me to something I didn't know back there, but that seems to be going on here as well.

Since some of the problem seems to occur on the unexposed parts around the sprocket holes, I suspect that insufficient fixing as well as insufficient washing and poor storage conditions have played a role in your case.

Sorry, I can't comment on ways to resolve the problem. My best advice would be to get in touch with a restorer of photographic materials. They deal with this kind of thing routinely.

Whatever you do, first do the highest resolution scans you possibly can before treating the original negatives.

At least you will have files you can deal with in the digital domain IF any recovery attempts destroy the images.

If some of the damage IS mold/fungus on the emulsion, then the damage is more than likely permanent; the emulsion was a food source for the biological growth. Removing it will probably remove any remaining gelatin under the damage.

It is possible that some of the yellow spots are caused by staining the negative with developer after copying. I write it from my experience - some of my old negatives are really stained by sloppy work. These stains can be cleaned. Stains from unclead fix - no chance. I tried recently with dirty, unfixed and poorly washed films...