Canna PK 13/14
Fast growing plants may need additional Phosphate (P) and Potassium (K). CANNA PK 13/14 stimulates floral development during the blooming phase, providing exuberant flowers and larger yields. Depending on the EC values and the type of growing medium used, this additive contributes to improved bloom and fructification. The form of the nutrients used requires a very small amount of absorption energy. This allows the plant to fully focus on blooming.
NPK Formula: 0-13-14
Lychee are certainly not fast growing. But I still think I'll give this a try.
Two ways to go about this one. First would be draining your reservoir, mixing up a nutrient solution with a NPK ratio of about 2-15-15. Let the plants use this solution for 24 hours, then dump and revert to your original mixture. This is what I would do, but I have lab equipment at hand and can easily determine the correct mixture. For the average gardener, I would mix:
16 grams Epsom salts
10 grams of monopotassium phosphate
5 grams potassium sulfate
1 gallon of hot distilled or reverse osmosis water
Let the mixture sit and cool, and if no cloudiness is present, foliar feed the under-side of the plants leaves. I would not recommend doing this more than once or twice during the plants flowering cycle, as potassium is deadly in very high concentrations.