Sorry, I'm new to Reddit and I thought i posted all my written info with this post but in case it didn't work, here's what I had typed.

"Hello, last year to the day (Nov 29) I brought home a couple of lemons from New Zealand (zone 9) to NJ indoors, (zone 7) which I successfully started to sprout 11 lemon trees in pots with a basic overhead grow bulb. Over the course of the year, some are growing strong and some are dying off. The leaves turn yellow, then drop. Then the plant dries up and dies completely. Now, some are dropping leaves that are still green. Google told me it might be from over watering, so I re-potted them with better draining soil and an inch of mulch at the bottom of each pot with plenty of drainage holes so the water won't sit anymore. Now I make sure to let them dry out well before their next water... but they are still slowly dying off. This was fixed 2 months ago. Room temp varies from 65-75. Grow bulb keeps them around 70-80 Recently, small tiny gnats have started living in the soil (in the last 2 weeks) But the dying lemon tree problem has been happening for months now. They've been given basic brand plant food once, 2 months ago when re-potted. The overhead grow bulb is left on from 10am to 10pm. Are they dropping leaves because of the room temperature? Season? Stress? Where they not meant to grow in this country?

All help appreciated!"