About your missing shrimp…..I’ve kept cherry shrimp for years. Had them in a tank with guppies and neons and pencil fish. No issues. Now I have a tank just for shrimp. I love keeping them.
I don’t think you said what kind of tetras are in there…..clown loaches will get way too big for that tank btw. If large enough now, they are eating the shrimp or the tetras are, depending on what type
Or, they are not getting enough food. The biofilm etc growing is enough for a while but I give mine some shrimp pellets every 3 days
The cherry shrimp do not eat each other
With all the live plants, are you certain there is no planaria? Because they leave a slime trail that is toxic and deadly to shrimp.
https://fishlab.com/planaria/#:~:text=White%20planaria%20are%20aggressive%20pre dators,than%20capable%20of%20killing%20them.