Check to make sure you have the correct pressure going into the membrane, but more importantly make sure its seated good and the correct membrane because those numbers sound off or like its leaking past your membrane.Tds is 387 ---415 coming in and 108 after membrane
And verify tds meter is correct try switch positions of the meters see if it reads the same .
Those are both high, incoming is high i would have a dual membrane for that . But even still with a 98% rejection rate that is still to high


