Combi boiler hot water downstairs but not upstairs
We have a combi boiler situated in the kitchen. Yesterday the water upstairs will only run luke warm. Water from the tap in the kitchen still runs extremely hot. The water from both the bath tap and sink tap (ran for in excess of 5 mins) does not heat up. Water from kitchen tap gets hot quickly ( I appreciate it is next to boiler). Previously took less than 10 seconds to get hot water through taps upstairs. Heating is still fine. What could be causing the water to be fine downstairs but not in the bathroom? Any help appreciated.