I have a creda shower that was installed new about 6 months ago, i dont know what model it is as there are no obvious markings, I do know that it is almost exactly the same as the 550c model. The shower has three power setting, low, medium and high. The low and medium settings have recently stopped working? Water still flows thru on the 2 lower settings but now comes out completely cold. The higher setting does still work, but to get it at a cool enough temp to shower in, the water pressure is so high it could strip the fur off a badger. How can i get my 2 lower settings working again????