Basically what has happened, is that one of our showers isn't providing the same quality water pressure it usually does. our other shower and all other taps are fine with pressure just except the one shower. we have tried putting on a new shower head (didn't fix the issue), we have had a plumber look at it to although he only really looked behind at the filter which had some dirt and little bit of build up but again that didn't fix anything. We are suspecting it is likely the shower mixer and think we may need to swap out the cartridge. We are on tank water so our pressure is usually way stronger with that compared to mains anyway. Any Help would be greatly appreciated.