New Kitten Won't Use Litter Box

Just got 5 month old female, not yet spaded. She keeps peeing next to the litter boxes (I have 3 and two adult cats). The boxes are scooped daily and I even​ got Dr. Elsey's kitten attractant to put in the litter boxes. She did use the litter box and few minutes later and had diarrhea. I think she may have used it once again that evening when I was at work with diarrhea. But she's also pooped twice on the floor by the boxes (regular stool then). If I set her in a box she immediately hops out. The animal shelter used those big pellets but she was only there 3 days before I got her so she couldn't be that used to it. I use the enzyme spray to clean the tile when she pees to get rid of the smell but she pees in different spots. I need suggestions please.