This is why you should never try to grow a tree entirely indoors. Even though you may have to bring it indoors for the winter, and even though you may stress it somewhat by doing so, trees love the outdoors.
As you may remember, this is how my Meyer lemon looked a couple months ago, post-root rot:
It had thrown out a branch of new leaves during the winter, which are the pale leaves a little above center of the piccie. But it didn't grow beyond that.
This is what it looks like now:
You can see the buds of new growth appearing all along each branch, and especially in the middle-top of the picture ... what looks like one wrinkled leaf is actually about a half-dozen leaves along a new branch, in the early stages of growth. Even the pale leaves it put out over the winter are starting to turn a darker green. Once I start fertilizing the plant, they will become the same color as the old leaves at the bottom of the picture.
This piccie is a bit blurry, but you can better see here how numerous the buds are.
Trees are meant to be outside. They love the outside. If you ever try to grow a tree, make sure it's outside as much as the weather allows. Citrus trees especially love full sun, which is something they can really only get outside ... even under glass, they are not getting full sun, because glass is opaque to ultraviolet.
Next week I'm going to have to bring the lemons back indoors at night, because it's supposed to get cold. Below freezing even, late next week (around Thurs-Sun). It's supposed to stay cold for quite a while. BAH! This utterly sucks.