We have a recent (3 years) hot water tank
The water locally is quite clean and soft
Previous hot water heater lasted 20+ years before the tank sprung a leak

When this tank was installed, the hot water flow was about the same as the
cold water flow
Since then the flow has been steadily slowing down where currently the hot
wate is about 60-70% of the cold water flow

What could be causing this ?
What can be done to solve this ?