Update 2
Shortly after posting my last comment, we lost 2 mote guppies and a Tetra . We can't really explain why.
In the end we think we put all of the issues down to having a bully fish in the tank. We havn't identified which one yet but we do beleive that the illness of the fish & the fish deaths were slightly unrelated or a bully fish decided to prey on the week.
Things have calmed down now and we haven't lost a fish in a few weeks now. We have completed several water changes and also moved the tank to another location to make way for a new one.
Several of our shrimp have been pregnant at some point but i think the fry have mostly been eaten which isn't a bad thing seeing as we have 9 already.