replace light bulb induces cynobaterica??

[mandarin man]

Hi,

I just replaced old RSM lights two weeks with new ones. I notice there is a small outbreak in the cynobacteria on sand and live rocks. Nitrate is less than 1ppm with ELOS test kit. 10-15% water change every week. I am not overfeeding, a mandarin goby, firefish, and two yashia gobies. Is it possible that changing lights could cause an outbreak in cyno?