Hi.

Newbie here looking for some advice.
I have copper pipes running off of my hot water heater that connect to Wirsbo aquapex plastic hosing. There is a cut off valve that is wide open before the Wirsbo connects to a spot where one hose goes upstairs to my kitchen sink (running great with good hot water pressure) and the other hose heads upstairs to my bathroom. The hot water pressure in my upstairs bathroom is horrible. I have a 2 handle faucet system in my bathroom sink and the hot water pressure is 10% of the cold water. In the shower, I can only have a decent hot shower for less than 5 minutes before the water turns cool and I can't turn the one handle system any more left to make it hotter. When this happened I checked my kitchen sink to see if I was indeed out of hot water but it was fine (I ran straight hot water for 5 minutes and it was still very hot).
This Wirsbo hosing is new to me (just moved into this house) and I'm at a loss as to what steps to take to try to fix this.
Any suggestions or tips would be greatly appreciated.
Thanks.