Fish dissappearing? (Yoyo loaches or BN plec culprits?)

[JuliaAndFish co.]

Hi, I have noticed recently that some fish have begun to randomly dissappear from my tank. Guppies, a molly, a female betta, and some tetras, and I have deduced that the only thing that could be killing them would be either my 3 yoyo loaches or my female bristlenose pleco. I haven't seen them ever be aggressive towards any other fish, and my tank has plenty hiding spots. I have searched the tank again and again, but I cannot find any sign of bodies or anything . The fish killed were healthy, and all fish are fed enough. My water parameters are:
Ph 6.8
Ammonia 0
Nitrites 0
Nitrates 10
Chlorine 0
If anyone can explain what the problems could be and what to do with it I'd be very grateful

 

[MaloK]

If your loaches are turning on your other fishes. You might want to feed them some more. loll.

What are the size of the fish targeted ?

I seen something like that in the past and it ended being a dragonfly nymph living under the radar.

Depending on the complexity of your decor... They can go unseen forever. they hunt at night and are ruthless facehuggers.

Note that it can take a long time for their eggs to hatch... At their birth they are literal fish food.

But if only "one" makes it's way. They are on another level of hunters.

Both times I encountered these in my tanks is because I used medication in despair of having no clue on what was happening.

And found them dying later in front of the tank.

Here's my latest encounter:

 

[GaryE]

Neither fish is a predator, but they are quickly working scavengers when a fish dies. That probably accounts for the lack of evidence, but not for the causes of death. Something is off.

 

[Fishfunn]

Throwing a question out there, could they get into your filter through the input?