Why Are My Neo Shrimp Dying?

[Jen]

I had two nano tanks that were about 3.5 gallons each. I kept mostly royal blue orange eye tigers in one and mostly painted cherry shrimp in the other. The parameters in each were ideal for the type of shrimp I was keeping in each tank. One morning I noticed that the cherry shrimp tank's filter stopped working. Since the tank was one of those with the self contained-filters I had to scrap the entire tank and get a new one. While waiting for the new tank to cycle my only option was to house the cherry shrimp in the same tank where I am keeping the Tigers. I thought this would be ok since I've read that cherry shrimp do well in a wide range of parameters when properly acclimated. However shortly after the transfer my neocaridina (neon yellow, painted cherry shrimp, black diamond) slowly began dying off while my OEBT and CRS were doing fine? From everything I've read caridina shrimp are generally more sensitive yet in my situation they are doing fine while my cherry shrimp are slowly dying off. What could be killing them? 

My parameters are:

ph: 6.8

ammonia: 0

Nitrite: 0

Nitrate: 5.0 ppm

KH: 2

GH: 6

I have UP Shrimp Sand under a layer of sand and the tank is nicely planted. I don't use C02. Though i do add about 3 drops of liquid fertilizer once a week. I feed them once a day with food ranging from blanched zucchini, shrimp pellets, BorneoWild, and occasionally add blood worms mostly to benefit the micro crabs.