very high tds water. ro question.

so I recently moved out of the city and I'm about 3 hours drive away from pretty much anything. I'm running my 50gpd ro system on well water. the tds of the well is 1456 ppm. after my ro membrane it's testing out at 226 ppm. so once it runs through my di it tests 0ppm. but my di only lasts around 15gallons until it's fully exhausted. I'm also running a booster pump on the ro system.

so I'm just wondering is this is normal? do I need to change my membrane? it's only 2 months old. any help would be appreciated.