hi being going for around 2 years now and think I'm looking at needing my 3rd membrane, my tap water is around 268 and now coming out of ro at 21 it's normally 12, the first ro was a hf4 4040 this current one is a hf5 4040, pre filters are replace every 3 months and membrane flushed every week I make around 400lt a day, water pressure is at 2bar, surely I should be getting longer than one year,any help on what could be wrong or is it just how long they last thanks