Question about RO membrane

[christyf5]

I bought a BWI SR-Elite 100gpd back in 2011 and noticed the TDS is starting to creep up. I guess the membraine is on its way out as I just changed all the filters and its sill higher than I'd like. My question is, as it is a 1:1 unit do I need to order a special membrane or is the unit itself what engineers the 1:1 ratio of good to bad? I found the original thread advertising it but BWI never really did say what the membranes were.

http://www.canreef.com/vbulletin/sho...light=1%3A1+ro