bamboo sharks issues

[btsride]

I have three bamboo sharks that were all hatched in my tank about a month apart from eachother. Last week the second oldest one started swimming around the tank all day and all night and not hanging out on the bottom like it used to. Two days ago the oldest one started doing the same. The oldest one is still eating but the other is not. Tonight the oldest one has red in his eye. The youngest one is perfectly fine with no issues. Should I give them a fresh water dip? Leave them alone? Or are they doomed? Thanks for any help

[Funkateer_1]

- What is the tank size and filtration?

- What have you been feeding them?

- What kind of substrate do you have? Any redness on their bellys?

[btsride]

Tank is a 180 gallon (building a outdoor pond for them now) I feed them yellow tail, krill, squid. Fine sand on bottom of the tank. No red on bottom of them