Golden Orfe (pregnant) death

Golden Orfe (pregnant) death

Observation - Golden Orfe (pregnant) death - UK and Ireland. Description: This is the second pregnant fish I have found dead in the last three days. This Orfe weighed 4lbs, age approx. 12 years old and had no obvious signs of injury as you might expect from a Heron (I cut the fish open to see if it had a roe, which it did). Th

This is the second pregnant fish I have found dead in the last three days. This Orfe weighed 4lbs, age approx. 12 years old and had no obvious signs of injury as you might expect from a Heron (I cut the fish open to see if it had a roe, which it did). The previous death was a medium/small carp which was also pregnant.
The only change to their environment is a addition of approximately 5% top-up of tap water (Kent hard water) in a 30 foot pond.

Can anyone help.