high tds

I've installed the smart buddie 150 GPD version with two NEW 75 GPD Dow membranes, run in parallel. After over 24 hrs of running, I get 13 TDS, even tho my tap water TDS is 310. The booster pump is pushing about 75 PSI into the membranes. Paradoxically, my old 100 GPD membranes in this parallel...

I currently have a 4 stage filter for my tap water that is 550 TDS. I run through DI resin in about every 2 months for my 25 gallon tank. My tap water is not treated with chloramines. My filter does manage to remove everything so my output is 0 TDS. Lastly, I use the RODI buddy booster pump...