Peace be upon you. The ruling according to Ayatollah Khamenei is that experiencing wet dreams during the day does not invalidate the fast. There is no obligation to perform ghusl (ritual washing) except for prayer or for actions that require it, such as entering a mosque. According to Ayatollah Sistani, the fast is not invalidated by wet dreams during the day, whether obligatory or recommended. Ghusl is only required for prayer or for actions that depend on it, like entering a mosque. May you be successful in all good.