More than likely it was imported from the source. It appears to be diatom algae, common in new tank setups and should go away in a few weeks. You should be able to rub it off if it is diatoms but it will probably come back. Otos may help too if you can find them.
If it came from me there may be some green fuzz on them too
I don't fertilize any of my shrimp tanks so the plants do get a bit of algae on them. The shrimp don't care so I try not to. I should probably add a bit of PO4 to those tanks though. It would probably help with NO3 uptake.
Overdosing or spot treating with some glut should get rid of both types of algae.