Your indoor temperatures may be cool enough to keep the tree from growing for a while, but the leaves in your pictures look fine. I wouldn't worry.
Here, where the trees grow outdoors in people's garden the temperatures range from 8deg.C at night to 24 C daytimes, with some days cooler, and some nights going a little lower as well. The trees will lose more leaves if we have a series of cool nights, and do not show new growth until it warms up.
It's possible that your grow lights will warm the area around the plant a little more, and give you new growth sooner when you increase the time the lights are on. But if not, just wait until spring. Modify your watering according to whether you are seeing growth, too. If no growth, water sparingly.
