Fish Sick Due To Stress?

[Schmill]

Stress does make fish susceptible to other diseases so there is possibly a problem starting in the tank.

If the red line on the cardinals is still fading and other fish are starting to have the occasional shake/ irritation, then it could be bacterial and protozoan. It is unlikely to be an internal bacterial infection but more an external type that is damaging the red line. The shaking/ irritation could be something like costia or whitespot that might be developing.
I'm not sure what is in the interpet internal bacterial treatment but if it contains methylene blue, malachite green, formaldehyde/ formalin or copper then it could be used to treat both these problems.
If the interpet medication doesn't have any of those ingredients then perhaps get something like Waterlife Protozin. But most fish medications have similar ingredients so you could try the interpet one first and see how the fish do over the next few days.

To work out the volume of water in the tank
measure Length x Width x Height in cm
divide by 1000
equals volume in litres

When measuring the height, measure from the top of the gravel to the top of the water level. If you have big rocks or driftwood in the tank, remove them before measuring the height.

Remove carbon from the filter before treating otherwise it will absorb the medication out of the water.

If you have any catfish or loaches in the tank then be careful with the medication. Most will suggest using a half dose for catfish.

Cheers Colin, presumably as I am hoping to have shrimp in the tank soon too I should avoid any meds with copper in them ?

 

[Schmill]

Another 2 dead cardinals this morning, and the others still looking washed out.

 

[Colin_T]

I am hoping to have shrimp in the tank soon too I should avoid any meds with copper in them ?

not necessarily. You can use copper medications but you just need to do lots of water changes before you add the shrimp. You can also put some carbon in the filter after you have done a couple of water changes and that will help remove the remaining medication.
There is a possibility that all the cardinals will die. The combination of stress and disease can often be too much for them and they just drop off.

 

[Schmill]

2 more cardinals dead when I got home + the Spotted Bulldog Pleco

 

[Schmill]

Last cardinal died this morning

 

[Colin_T]

not good sorry to hear they didn't make it.

 

[Schmill]

1 x Albino Cory

Now treating the rest of the tank for a Ich outbreak, presumably brought on by the stress of the shipping...