Seen this before and it's all on your water. Not lighting unless your bulbs were old!!!!!! Then that'll cause your algae on top of bad quality water.

I hate testing my tanks so I do weekly water changes of 25% or more but nanos are prone to spikes depending on how you feed and what your keeping. To much phyto and it can make the parameters jump a bit and if its going up daily well then you know what your doing wrong.

I would just start doing more water changes and start from there.