I noticed some yellowing needles on my Afghan Pine Tree toward the bottom inner branches. It was bought and planted three months ago at 5' high and 20" wide. Where there were two leaders on top there are now nine. I deep soak it with a soaker hose every 4 days for 3 hours and give it one gallon of 20-20-20 liquid nutrients every three weeks. Is there anything else I should be doing or not? Would appreciate your input.