Loss of flavour in the transition from stiff to liquid sourdough

Hi, I convinced a lot of my friends to convert their stiff sourdoughs from solid to semi-liquid form because of the ease of use, but now many of them are complaining of the loss of flavour of the bread produced with it. They generally do a poolish with 100 gr of water, 100 of whuie flour and 10 of sourdough, then they prepare the final dough with the rest of the water, salt and flour and various phases of proofing. The benefits they see are a much softer consistency and a longer lasting, but the taste is very decreased. What can be the cause of the loss of flavour? Is there a way to restore it while still keeping the liquid form of the sourdough? Thanks.