I have 3 lemon tree seedlings that I’ve been growing since July 2017. Two of the seedlings are doing fine, but this one recently started to take a turn for the worse. The leaves have slowly been falling off and it hasn’t grown in at least 2 months. The stem is still green and I can see a tiny new green leaf growing at the very tip. I recently bought Jobe’s fertilizer to help give it a boost. Is there anything else I can do to help revive it?