Problems with shrimps and snails

Hey guys, I have been keeping a 10g tank for almost a year now and would like to know why I am having trouble keeping shrimp and snails. A hitch-hiker pistol shrimp made my first cleaner shrimp's insides implode, then after I got that little punk out the next cleaner I bought died a couple days later. That was a good six months ago, now just last week the snail I bought went off the deep end. I have two hermits and an awesome little urchin doing great, btw.

From what I've read here it's likely either a copper problem or a rapid acclimation to the tank. Could I cancel out the copper scenario being that a pistol shrimp lived in my tank for at least 4 months before I removed it?

Also my nitrate levels are a high, around 30-40ppm. I'm doing what I can to lower them. Everything besides that is normal.

Thanks for your help!