I have had to cut 1/6th of the stems after it had not been watered for 11 days (don't blame me). Still, after three or four days some other leaves don't look as they used to yet. Spring is coming and seems to be a good moment to fertilize it. Should I do it as soon as possible or would it be to stressful for the plant to pass from a drought to "over-stimulation"?
The leaves you've got present now probably will never return to their former state of glory because they were subjected to a period of serious drought. The most important thing is the plant still lives, so keep it well watered, though not waterlogged - and there's no reason not to start feeding it now, but only at normal rates and frequency for the product you're using.