Help me identify these stains, please!

[Dusty Negative]

Hello.

So, I printed up a few 120 negatives using 11x14 Ilford MGFB Art 300 matte paper....and happened to notice some terrifying stains when holding up the prints to a strong backlight.

I used fixer that was still "good" at least as far as a hypo check test (the droplets) indicated, although the fixer had definitely been used on multiple prints previously.

I also was using rather old selenium that I had been replenishing over time.

*So* I am wondering if anyone can identify the stains and help me understand whether:

1. The fixer is the culprit, because while still capable of fixing, had too much spent silver that I did not sufficiently wash out, or;
2. The selenium is the culprit, because it was old and had all kinds of who-knows-what floating in there, that I did not sufficiently wash out, or;
3. A combination of the two, or;
4. Some other issue.

Here's the print. Again, these stains are only noticeable in a back-lit situation. They do not show up at all under normal viewing conditions.

Thanks so much for any thoughts/suggestions.

 

[Dusty Negative]

Ok, well. Maybe this is the answer.

URL="https://www.photrio.com/forum/threads/question-regarding-poor-print-wash.183311/page-2#post-2409370"]Question regarding poor print wash[/URL

 

[Dusty Negative]

Right. Sergeant Major marchin’ up and down the square!