Flushing with a very very light solution (a solution with very light fert strength) won’t harm your plant.
Flushing is a great means of flushing toxicity out of soil. If you haven’t been getting any runoff then your ph might seriously be off. When the ph is out then your plant can’t take up nutrients efficiently.
Actually, I would flush with an Epsom salt solution. There’s many ways of flushing. Some might use a root stimulant in the French solution to minimise stress.
Last message, promise