I had two of the Haunted Dolls at max posts in my slots- went to Chloe and turned in 5 stones and it levelled both items.
Just thought staff should know about that.. Seems like it might be exploitable!
edit: As a sidenote, I also had a maxed Frankendoll but it did not level that at the same time- I think the items with the same name were maxed, leaving the other with just the points and still needing the stones.