Head injuries, fungus, and excess slime on new Wallace’s shoehead catfish, advice?

[fishhead0103666]

Have you tested your water?

Yes

If yes, what is your ammonia?

0ppm

If yes, what is your nitrite?

0ppm

If yes, what is your nitrate?

20ppm

If I did not test my water...

1. ...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.

Do you do water changes?

Yes

What percentage of water do you change?

71-80%

How frequently do you change your water?

Every week

If I do not change my water...

1. ...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.

Hello, I’ve recently acquired some Wallace’s shoehead catfish and on the new additions I’ve noticed that some of them have a small amount of what I believe to be fungus on them, some have minor head injuries on the same area from fish to fish, and one or two has excessive slime coat shedding. If possible I’d like some advice as to my next steps. The first one is showing the believed fungus on the pectoral fin and the second one is showing the head injury.

 

[duanes]

These cats prefer pH below 7, highly oxygenated water, with concentrated tannin stained conditions that keep certain bacterial and fungal infections to a minimum, and they prefer low nitrate conditions that hold infectious bacteria low. (soft water species have different immunity than thosse used to hard water)
If they have been held in harder water, where bacteria common to higher pH, hard water is common, this may account for the infections.

If it were me, I'd do enough water changes to keep nitrate below 10 ppm, and add leaf litter, peat moss, or other tannin producing agents to tint water tea brown.

Where I collect Pimioodus catfish, they are almost always found in tendem with leaf litter conditions that promote brown stained water, even in the high pH, harder water where I collect..


Below the right tube is a test of nitrate concentration where they are collected.

 

[Fallen_Leaves16]

The injuries look superficial and I wouldn't worry about them too much- preventing infection is far easier than treating it, and any attempts to treat the fungal issues will probably be enough to keep it from worsening.
My main priority in dealing with woodcats is to get them to eat something first... yours do look rather skinny and I'd personally be a lot more at ease if they had some food in them.
You're certainly far better-versed than I in dialing in care for these guys, but I do wonder if live feeder-fishes and shrimps would be favoured. Supposedly they do well on those, at least until they transition to something else.... wonder if they'd damage or harm the fishes at rest, though.
Is the fungus the odd dark fuzzy streak on the anal fin? Picture's a bit blurry and I couldn't see anything on the pectoral... if it is, then I wouldn't be terribly worried- a touch of salt should clear it up, or a dab of methylene blue on it (which should be fairly easy to administer given their activity- or lack thereof). Just making sure it doesn't appear to spread aggressively is of priority, I would think.
Only problem is they don't seem to take too kindly to salt, and it would be a bit counterintuitive to softening the water, I think.
I agree with Duane in regards to softening the water substantially and adding humic substances. Tannins do help stave off infection to some noticeable degree IME.
Unfortunately not too sure about the slime-coat issue, as I've not been able to witness it myself. I would assume good water would go a long way in resolving it, though.