300US gal = 1134 ltrs. 650ltrs = 172US gal
your system is only working at slighty over half its capacity, factors such as inlet tds and inlet temp play a role too - make sure your sediment and carbon filters are changed regularly and backflush the membranes regular also. You can manage with this level of production if you have at least one 1000ltr IBC storage tank, although your ro will have to run 24hrs a day and most likely 7 days a week to keep up with you.
On the other hand you can upgrade the 3 membranes to 150USgpd membranes, but at that price I'd rather go for a merlin which is rated at 720GPD, although you will need a di after this.