I transplanted my lemon tree from a pot to the corner garden bed. Since then, it has a lot of flowers and has lots of lemons. It is only just over a meter high but seems to be stagnated now, as the fruit has been the same size for a couple of months. I water and feed it, but the fruit seems more like limes than the huge lemons it previously produced.
Soil for citrus trees should be slightly acid, not alkaline, but above all should be well drained. They don't like to have their feet wet, so if there is a risk that when you water the tree the water will sit around and flood the roots then the tree will demonstrate its unhappiness by not growing or shedding leaves. Quite possibly when you moved the tree from a well drained pot to a less well drained garden location you continued to water it as if it was still in the pot and consequently gave it more water than the soil was capable of dealing with. You can test this by driving a stick into the soil close to the tree and then pulling the stickout to leave a deep narrow hole, then use a dipstick to see how far down the water table is. Standing water at the bottom of the hole is a problem for the tree, which should be moved to a higher spot or watered much less frequently - whatever allows the roots to grow freely into soil which always has some water with lots of air.