What are you keeping your calcium level at? Depending on your ca level and the quality of your seed rock you should see a lot more coralline IME.
In my last build I also used Marco and LR at a 50/50 ratio, I kept my ca at about 450 and after four months my tank was swamped in coralline. If you want to speed the process up, you can just take a nice piece of purple rock and scrape the coralline off with a sharp edge letting the scrapings fall into your display tank, keep you levels good and in no time at all youll be scraping it off the glass on a weekly basis.
Day one.
Seed rock mixed into Marco rock.
One month, the Marco started to speckle with coralline.
Two months, there wasn't much white rock visible.
Four months. Coralline everywhere.
