Weather loach injured, health quickly declining. please help

Tank
What is the water volume of the tank? 40 gallons as a grow-out for the loaches
How long has the tank been running? about 2 months
Does it have a filter? yes
Does it have a heater? no
What is the water temperature? 72 farenheight
What is the entire stocking of this tank? (Please list all fish and inverts.) 3 weather loaches (all less than 4 inches), 6 mosquitofish, and a handful of malaysian trumpet snails

Maintenance
How often do you change the water? weekly
How much of the water do you change? 10%
What do you use to treat your water? imagitarium dechlorinator
Do you vacuum the substrate or just the water? I vacuum substrate and remove organic matter by hand as needed

*Parameters - Very Important
Did you cycle your tank before adding fish? yes
What do you use to test the water? API master test kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 5ppm
pH: 7.4

Feeding
How often do you feed your fish? 2 times a day
How much do you feed your fish? a small piece cut off of a frozen cube
What brand of food do you feed your fish? san francisco bay brand
Do you feed frozen? yes
Do you feed freeze-dried foods? not any more

Illness & Symptoms
How long have you had this fish? a little more than a month
How long ago did you first notice these symptoms? earlier today when he wasn't interested at feeding time
In a few words, can you explain the symptoms? quick breathing, inactivity, red dots/spots on his tail
Have you started any treatment for the illness? no
Was your fish physically ill or injured upon purchase? no
How has its behavior and appearance changed, if at all? noted above

Explain your emergency situation in detail.

I noticed my albino weather loach wasn't interested in food earlier, and seemed to lay around the tank while the other 2 loaches were active and enthusiastic as usual. I left for a while, figuring I'd keep an eye on him. when I just now checked on him, he was laying on his back in a plant. I touched him to see if he'd swim away, but he didn't. he's still breathing but I'm able to handle him without him reacting. I took these pictures of spots on his tail I didn't notice before. I'm holding him very gently and the picture is taken through the tank

 

Hi, I'm sorry but red spots like that are usually a sign of septicaemia or maybe a parasite infestation & given that it's so lethargic & not eating I don't think it will recover, do you have a QT tank you can put it in?

 

Hi, I'm sorry but red spots like that are usually a sign of septicaemia or maybe a parasite infestation & given that it's so lethargic & not eating I don't think it will recover, do you have a QT tank you can put it in?

thanks for the reply. he unfortunately passed away last night. Is there anything I can do to make sure the rest of the tank stays healthy?

 

thanks for the reply. he unfortunately passed away last night. Is there anything I can do to make sure the rest of the tank stays healthy?

Sorry to hear your fish died. Keeping the tank water as clean as possible with regular water changes of at least 50% is probably the best medicine you can give them right now & keep a close eye on them for any changes to how they look or behave usually, if there are any issues give us a shout out as soon as possible & we'll do our best to help.

 

Sorry to hear your fish died. Keeping the tank water as clean as possible with regular water changes of at least 50% is probably the best medicine you can give them right now & keep a close eye on them for any changes to how they look or behave usually, if there are any issues give us a shout out as soon as possible & we'll do our best to help.

will do. should I stick to weekly water changes or should I do them more frequently? I appreciate your condolences