Don't know if this has been reported but the "Passive Growth Crystal" doesn't work if you have multiple equipped to different party members. I have one equip to each of the three, but only Leah is getting the growth. Then, when I took of Leah's crystal, that's when Valorie's Crystal starting working. Then, once again, once I removed Val's crystal, Sanura's started working.
I wonder if it's a race condition or something bugged about the game's condition/status ticks. I didn't have any problems with multiple Passive Growth crystals, and even tried equipping them in similar (first crystal slot only) and different (first slot Leah-second slot Valorie-third slot Sanu) equipment slots to see if I could get the bug to occur on my copy.