I have a Colorado blue spruce that I have now had for two years. The tree was super healthy when I got it, so all I did was prune and style. It was doing really well until I fertilized it this spring, then it seemed to start to yellow at the apex. I removed all the fertilizer and it seems to have recovered. I would like to know how and what people are using to fertilize there spruce trees. (I used Doctor Earths organic fertilizer.) I would like to fertilize here soon as I have heard fall is the best time to add fertilizer to your trees, as to help set buds for the next growing season. I am just nervous the same issues will happen again. Once suggestion was to use Osmocote Plus, as it has worked for most of my other trees. Any input would be appreciated.