There are many factors that effect floc times - milk quality, milk proteins, amount of culture, type of cultures, ripening time, pH at rennet, temperature, etc. Do you test pH during your makes?
With Parmesan, you need to also use TA61. The LH100 is not a primary lactic acidifier. The TA61 ("Thermo Acidifier") does the main lactose conversion but is incomplete so the LH100 comes in to finish the job.