Ok... I went to petsmart (

) yesterday and got two baby guppies and 4 ghost shrimp, I acclimated them and checked the water parameters to make sure everything would be fine...
this morning I woke up and I noticed that none of the shrimp were within sight, except one which looked white and was lying motionless in the bottom., it had died overnight. I went to get my net and take it out but before I could do something my big mystery snail had almost finished eating it
I dont know where the other shrimp are... I saw only one sitting in one of my fake plants and it seemed fine. I just dont want any more to die... any ideas on what happened? maybe my gourami killed it

? (I dont think so since they are so fast and my gourami so slow) am so confused since my water is so perfect:
ammonia 0
nitrite 0
nitrate 7ppm
pH 7
any ideas on what could have happened?