To start with, I am the furthest from a green thumb, but I am trying desperately to learn and figure out how to keep some plants alive! :(

I got this little lemon tree over the summer, planted him in a nice big pot, he sat out in our front yard with lots of bright sunshine and regular watering. Then once it started hitting 'fall' weather (we're in ATL GA) 85* during the day, then 40/50 at night, I decided to bring inside since the temp swings were so drastic. He is now in our guest room, right under a south facing window, and recently added an LED grow light, I keep about 1-2ft from the plant.

After coming inside I noticed all the leaves started curling in on themselves, but all green, not any crunchy/ brown/ yellow etc they all seemed happy and healthy except curled up. I was afraid I was over watering at this point (I've made this mistake with several other plants) and or not enough light, so I halted watering for a few weeks and then invested in the light. Slowly all the leaves started falling off, just as green as they started. - Still not watering trying to let the soil dry through.

The light has been going for a few weeks now, a solid 9 hours per day usually, one leaf left and honestly the worst looking leaf! Brown spot and all. Since the new lamp, one of the lemons has started turning yellow and the other I just noticed with a little grey/ tan patch at the stem. I've finally given in the past few weeks and started to give a little water, but now I'm noticing the tip 1inch or less of some branches are turning brown/ black and seem dried out/ dead.

I just bought citrus fertilizer, and some perlite, planning to take it all apart this weekend and try to get the soil to drain better and replant. Please let me know your thoughts, I can't tell if I've over or under watered at this point and I don't want to give up!!!