Best tip would to to cultivate a decent fungi and bacteria colony in your growing media. You need to feed those guys with sugar and they help process food for your plant. Blackstrap molasses has the most nutrients in it as it's at the end of the refining process. 5-15ml molasses per litre, depending on the strain, once a week in soil works for me.
You can use other syrups but don't use antibacterial syrups like honey without checking if it'll destroy your beneficial bacteria colony.