Why are my Lavender Flowers Turning Brown? (3 Solutions)

Lavender blooms may become brown as a result of frost damage, a fungus (caused by moist soil), or a natural process when the flowers mature into seed heads. A fungal illness is probably present if the foliage is also becoming brown. A late frost may harm the delicate flowers if the leaves appear intact, but…
Source: https://thegardenhows.com/why-are-my-lavender-flowers-turning-brown-3-solutions/