Fish Keep Dying. Parasite Or Please Help Determine Cause?

I had 4 neon tetras, 3 guppies, a few ghost shrimp, and 3 snails in a 10 gallon. All 3 guppies died within the past 48 hours. Only one showed a sign of illness (had clear poop but I read somewhere it could vary since I fed bloodworms the day before) and it was one of the first to die so I wasn’t able to treat it. The other two swam around normally until they seemed to be losing control and then just flipped over/bent and died (a few hours apart).

The first one was found in the morning with the ghost shrimp eating it (to the point where it had a hole in its stomach). I still haven’t figured out the exact cause of the deaths and was wondering if anyone could help determine? I also noticed the belly’s (underside) were red after they died. Additionally one seemed to have fin rot a few days back so I had been treating the whole tank with melafix/Pimafix for 3 days to be safe. The first ones tail was significantly smaller when it died and the second ones fins were kind of blackened but everything else seemed normal.

It seems too much of a coincidence that only the guppies died and all my water reading were fine 0 ppm ammonia (until all 3 died then .25ppm ammonia), 0 nitrite, but 20 ppm nitrates (before fish died) seemed odd even tho I did a water change less than two weeks ago and after they died it rose to 40ppm so I did another water change.

After the water change I found some sort of insect that looked like a baby ghost shrimp from far but idk if that had anything to do with the deaths (attached picture, if anyone can identify itd be great). It could’ve just been something that got in while I was changing the water but I just wanted to make sure.

I attached pictures of the dead guppies if it helps identify. Honestly, I couldn’t even tell if it had anything to do with fin rot since it was being treated (and typically doesn’t wipe out fish that quick), but it could’ve been the clear poop, melafix/pimafix, the insect, a rare coincidence or any other parasites? I’m really confused and would like help on what to do next and if my neon tetras, shrimp, or snails could be in trouble.

 

That's looks like a dragonfly nymph. So without you explaining anything about the tank aside from it is cycled here's my theory... mom dragonfly laid eggs in your tank and then came back later after they hatched and killed the guppies so the babies had something to eat(something they never ever do).
https://www.fishlore.com/aquariumfishforum/threads/aquatic-emergency-template.376562/
If you follow the link and fill out the info we could come up with other more reasonable ideas tho.

 

Have you tested your ph level? I had fish behaving oddly last year and got red and sore looking bellies...my tap water ph had dropped after a big storm. Too low a ph is like acid to fish, too high and it burns them too. A pinch of baking soda raises ph (temporary fix) as does crushed coral. Different leaves that leach tannins lowers ph. Important to remember that big swings are worse than acclimating your fish to the ph of your own water, even if it's not ideal for the breed. It's worth testing.

Add: some meds such as melafix can lower the ph during use

 

Are you sure nothing got into the tank like a spray or something?

 

Yea I’m sure no spray is in the tank and my ph is around 7.2-7.8. Doesn’t change dramatically but maybe after water changes since my tap ph is 7.8, but if it was the ph wouldn’t the tetras die first since they’re more sensitive? Also found a neon tetra dead today so I’m scared that others could be at risk.Also had tank for almost 2 years now and went over many obstacles such as ich like a year ago but nothing like this. So it’s fully cycled I just don’t understand what’s wrong.

 

White poop is a sign of internal parasites- clear poop is usually stress or constipation or both.

There is a disease called redspot disease which is fungal. I'm not very knowledgeable about it but it might be worth looking it up.

The black fins are a mystery..never heard of that before.

Until you figure it out waterchange waterchange waterchange and watch your parameters... that should slow it down if nothing else. I have found waterchanges solve almost any problem I've ever had.

I'm sorry you're going through this and hope you figure it out without further losses. Please do keep this updated? We learn from everyone's experiences. Fingers crossed!

 

Yes I’ll keep you guys updated thanks for the help. Also just spotted another bug in the tank I took it out and took pictures if it could be identified that would be great . Could it be another dragonfly nymph even though it looks kind of different? Also I made the post for the fish emergency template.