Riddle try 1

 Darkness grows day by day,

 for what it consists of I dare not say,

 it settles down in deep,

 especially when I sleep,

 in dark and moist it thrives,

 rampant spread destroying lives,

for so small it contains many,

 as it spreads oh so plenty,

 sometimes hidden some in sight,

 what it carries is a serious blight,

 if you have it you may not know,

 for it does not always show,

 what it is cannot be sung,

 as it settles in your lungs