@OP: You've probably made the same mistake I have in the game referred to in
this thread
What I did wrong there was that most of my colonists were located in a handful of fairly large cities during my LB-generation phase.
That's bad, because large cities have a lower maximum RS and once you reach that maximum you cannot increase it anymore, in turn 'capping' that city's contribution to global RS.
There are only two solutions I know of once you encounter this issue:
1. reduce total population (since it's a divider in the calculation of global RS)
2. build more cities and generate additional RS there. You should continue to generate LBs in your initial cities as well though, otherwise global RS will decay.
Ideally you'll want to keep your cities limited to 15 citizens at the very most during the LB phase and keep total population in check as well. Either that or generate LBs from the very beginning of the game, although that option theoretically leaves the king more turns to add to his REF. I'm unsure whether the latter option would necessarily result in a larger REF though, as I have no idea how the amount of units added to the REF, or the precise turns when they're added are determined.
Anyhow, I've opted for the former option in my recent games and increasing global RS to 50%+ is an absolute breeze now, while the REF is more than manageable.