Hi. I have a normal shower and an overhead rain shower that are all connected through one unit with two handles on the wall to switch between showers. A relative took a shower and instead of turning the unit on the wall off they just turned both taps up to stop water coming out of any shower. I turned the unit off a couple of hours later. Anyhow now when I switch on the shower it is only cold water running and will not give hot water out. Can anybody think what is wrong? Thankyou.