We just bought a Meyer lemon tree from a nursery in Louisiana which has leaf spots (http://www.starnurserybellechasse.com/products-page/citrus-trees/meyer-lemon/). I asked if they treated their citrus with insecticide before shipping. The reply was that they treated with whatever Louisiana required. Can you see if this is a citrus psyllid indicator or just typical pesky scale? I can send a sample if needed. Tree is indoors now and I don't want to put it outside until I know. There is no way to upload photos here that I can see. Image is at: https://photos.app.goo.gl/DyYLekbTa16WsVxw8 Ed Kornegay
Montgomery County Maryland
We don't see anything of concern on your citrus leaves. It is not of insect origin- not psyllid or scale.
It may be residue or markings from fertilizer or other applications.
Often people who overwinter their tropicals as houseplants find that putting them outdoors for the summer greatly helps control insect or disease issues that arose indoors, as beneficial insects help us out, along with increased humidity and air flow.