RO membrane question?

[Canadian Man]

Well I have had my Kent ro/di unit for about 2 year's now I guess. I recently just had to replace the DI cartride part of the unit. I replace the Prefilter and carbon every 6 months religiously.

After filling the 230 I replaced all 3 parts (prefilter,carbon, di) cartridge. The DI cartridge has allready started changing color and it's about 1/2 and inch up now. This concernes me as the origional DI cartridge lasted 2 year's before it was color changed up to the top.

What's up with this?
Is it time for a new membrane?
Is there anyting to do to the old membrane to restore it somewhat?

I have been restricting the output waste water from the membrane for the past few month's to not waste so much water. so I cut it to about 1/4 of the output and make sure I flush the membrane more often(like 2 times a week).

some insight would be helpful.
Thanks