Is there a difference between leek and sad cursive script?

It makes no difference.

Of the five styles of calligraphy, cursive script is undoubtedly the simplest one. Many of our simplified characters are from cursive script. Due to the simplification of cursive script, there is a very interesting phenomenon that two regular scripts may use one cursive script at the same time. For example, the cursive script "green" and "fate", "leek" and "sadness" are all written in this way.