kuhli loaches and cory's dead dying HELP!!!!!

[1fish2fish]

Last night we went to feed the fish and noticed that one of the cories were dead.  We couldn't find the other one then after hunting found that one floating at the top of the tank in the back.  Both kuhli loaches (one who is like 9 years old) were looking pretty bad.  Their heads were red and they were gasping for breath.  The pleco per usual seems unphased.  As of this am both loaches were still alive, doing the same thing, however last check the smaller loach had expired.  I have been searching since last night for a disease but the only thing I have seen is "Red Pest"  and I am not sure that this is what it is/was.  Any and all  advice is needed.  Should we do partial or total water change after the other one dies/recovers?  Is this something that will kill the pleco?  That fish is at least 11 years old, I would hate to lose it!  Should we treat the tank with anything?  Please help!!!

Angie

 

[RedTurquoise]

What are your ammonia, nitrite, nitrate readings? Live plants? C02 injection? Temperature? Tank size?

Physical signs, anything out of the ordinary? Breathing heavy, clamped gills?

Water change is always good! Using aged water is the best but do a 15% water change! No meds yet until you know what the problem is!

 

[1fish2fish]

All levels are normal, tank size is 30 gallon, filtration is from eclispe.  The loach is laying on it's side breathing possibly a bit heavy, hard to tell as I don't really see the loaches for extended time periods, they spent most of their time under a rock clump.  The red color has faded since yesterday.  This came on suddenly as all the fish including the now dead ones, were acting normal and eating yesterday morning.  Did water change.

 

[clothahump]

It would be good to get some accurate readings, what is normal?
Sounds like a Toxin or Ammonia problem possibly/probably connected to the water change.
Does your water supply contain Chloramine?
When you prepare the water do you use a good Dechlorinator that will also get rid of Chloramine?
Has the water authority flushed the main to kill off crustaceans?
The last one is my best bet.

 

[1fish2fish]

We are on well water so no chlorine etc in the water.  The fish got sick before the water change.  There has been nothing added to the tank, nothing taken away and nothing changed.  There are no plants and we haven't add new rocks or anything like that.  This was out of the blue which is why  I am so confused.  

Thanks for any help!
Angie