Have you ever used any meds in this tank? If so, what exact meds? (doesn't have to be copper based)
Do you happen to know the seller's water parameters?
What method of acclimation and for how long did you acclimate them?
Neos are generally hardy and can adapt to your water params, but if they weren't acclimated gradually and their water chemistry was suddenly changed drastically, it can cause issues (though they would have normally died within the first couple days or so).
You haven't used any Excel or Osmocote+ right?
How's your water changes? (how often and what % water replaced)
Besides the tissue turning white (necrosis), is there any color change (copperish color) to the tissue or shell?
If you had low oxygen levels, you would see the shrimps hanging around the water surface a lot.
If you suspect bacterial infections, you can use Tetracycline, Oxytetracycline (better) or Minocycline (best of the 3), all of which are shrimp safe.
Another member posted a link to water parameters. If doable and you can't figure out what's going wrong, I would try those params (you can cut your GH, KH, TDS by mixing R/O or distilled water). While plenty of people have kept their Neos in similar or even higher params than yours, those shrimp may have had more time to adapt slowly. I'm not sure what all you have in your tank, but the shrimp, otos and even the plants would appreciate cooler water.
Seaweed (Nori) has a good amount of Iodine in it, which can help with molts.
No meds ever used in this tank.
This is the second batch to die in my tank. Both from different sellers.
I do a 20% water change every week or every other week. It's not this.
No excel, no osmocote.
No color change on the shrimp except tuning a little purple after death and then losing color. No copper coloring. White band is appearing on the shrimp as shown above.
I haven't tried any meds.
It's not an acclimation problem. I've been doing this for years. Both sets of shrimp were acclimated.
Not a temp problem. I have AC. My tank is regulated by my Apex, heater and fan. It never varies more than 1 degree from 77.
I've raised my Eheim output and have better oxygen in the tank now with less surface film. I'm also running my Eheim skimmer more often. The problem wasn't bad to begin with.
Food i've listed earlier in this thread, but for now i've been feeding Kens premium veggie with calcium.
I use prime every water change, dosed according to the instructions.
Only other fauna in this tank is 3 ottocinclus which are doing fine.
I added moss a while back on some SS mesh. I've contacted the sellers and the moss was not dipped in anything before shipping. Possible that the SS mesh had lingering chemicals and it wasn't washed off?? I quickly rinsed them before use.
I'm beginning this is something random like a contamination of soap, cleaning supplies or something else from the air or from a bucket.