Help! Black spots Everywhere

Hi All, I am newbie in planted aquarium. Currently still in fishless cycling stage for 20 days. Mine is Fluval flex Mega 30 gallon tank.
I noticed that there are black dots on most of my plants recently. But I am not sure if it is BBA or not.
The only difference is I added second Aquasky light week ago, but the light is not strong. In the beginning I thought it is nutrient deficiency and added Flourish nutrient.. Today I saw the situation gets worse.
Could you please help me see if it is BLack beard algae, spots algae or something else? It looks bad.
Thank you guys