Yeah that could definitely be killing the shrimp. Try a slow 25% water change.

Seems to be 3ppm

That's really unfortunate, I'm sorry to hear that. What's the exact ammonia reading?  

I just grabbed a cup and added the water I normally use for the shrimps, added salvinia natans and put both pandas left in there. One is dying, the other is still active. 

I'm sorry I thought I had answered. Ammonia levels were low but o tested today and it was really high. I've kept doing water changes every day but 20-30%.  I just did a 40% or so. One panda died. Ammonia must be the reason. The 2nd panda is already slow and dying. I don't have another tank sadly.