Prints getting dark

[NandoTheNinja]

Hey guys, me and my girlfriend just started printing on my own darkroom. So she had an assignment from one of her's university class and we thought about doing some prints, and we have done them. We followed all the instructions on the paper boxes and chemical bottles so we thought we should be fine. But turns out some of the prints we have done are starting to get grey stains. Do you know what is causing this? How can i prevent it and can this be removed?
Thank you!
Ps.:We used fomabron mate paper, fomatol developer, adox adostop stop bath, and fomafix fixer.
P.p.s.: It's hard to see on tje photos but is pretty notisable on person.

 

[Hatchetman]

I think improper fixing is the problem. Not long enough in the solution or the solution was exhausted. You really need to be careful with how many sheets you can use in a fixer solution. Tests your mathematical skills.

 

[mike rosenlof]

I agree with improper fixing. Light sensitive silver salts remained in the paper emulsion after fixing and have darkened with light exposure. You can probably halt more change by re-fixing the prints in fresh fixer (I think it will, certainly won't hurt). There are ways to bleach the prints, but you're probably better off to re-print if you're just getting started.

 

[Jake Mongey]

+1 improper fixing - when i first started 2 years ago i never took fixing seriously enough and I have no work or negs to show from that entire period

 

[M.Hilo]

Indeed the fixer could be the problem. Check your dilution too! Perhaps you got it wrong. Fixer should also be about 20 degrees (68 F), like the developer and stop bath.
If your fix was fresh and the right temperature and you kept the prints in the right time, then you may have too strong lights, or the lights too near to the developing tray in particular. Or your enlarger is leaking light . . .