Growing More Purple Coralline Algae

Hey guys! So, I have had my 100 gal with 2 48" Current USA Orbit Marine LED's for about 18 months. I was a typical newbie back then and was using treated tap water, of course I have an RO/DI now.... but needless to say I didn't have the most stable environment. Now after I have learned so much and moved to a place with a legit LFS, my tank is doing lightyears better than it was. Parameters are excellent and everything in my tank is super happy. I have specs of purple coralline algae that are on my LR but I really want it to encrust. I used purple-up sometimes and my iodide, mag, and cal levels are great. What else should I be doing to really get this stuff to grow? Is it just a matter of patience with stable parameters? If my phosphate levels are very low will the purple still grow? I'd love to hear what you guys, the experts, have to say. Thanks!!