The creek probably had waste in it that was toxic enough to contaminate your water. I'd do a quick 50% WC before anymore casualties occur within the next few days.
As for plant food... what do you dose? If you use excel, then it can kill shrimp. I was giving my new plants "excel baths" and didn't bother rinsing the excel off before I added the plants into my CRS tank. I ended up killing 2 (or was it 3...) CRS this way. Technically, I indirectly overdosed the tank due to the plant-bath.
Dosing nitrates too much can certainly cause some deaths too. Personally, I don't dose nitrates in my shrimp tank. I used to... but I don't want to risk it anymore. I rarely dose ferts in shrimp tanks now due to bad experiences. And when I do, I dose half of what is recommended, if not less.
Of course, there are some people who have success with dosing ferts and even overdose on it with no casualties. If you plan on dosing ferts, then I would suggest you start at half dose, then slowly work your way up to acclimate them. Shrimp are much more fragile than fish, that's for sure
As for plant food... what do you dose? If you use excel, then it can kill shrimp. I was giving my new plants "excel baths" and didn't bother rinsing the excel off before I added the plants into my CRS tank. I ended up killing 2 (or was it 3...) CRS this way. Technically, I indirectly overdosed the tank due to the plant-bath.
Dosing nitrates too much can certainly cause some deaths too. Personally, I don't dose nitrates in my shrimp tank. I used to... but I don't want to risk it anymore. I rarely dose ferts in shrimp tanks now due to bad experiences. And when I do, I dose half of what is recommended, if not less.
Of course, there are some people who have success with dosing ferts and even overdose on it with no casualties. If you plan on dosing ferts, then I would suggest you start at half dose, then slowly work your way up to acclimate them. Shrimp are much more fragile than fish, that's for sure