I'm getting the same thing on a couple of my plants (see attached images) in my research I'm finding out it could be a number of things, such as over under feeding, lights to close, not enough light etc. the list goes on, It's something we are going to have to pinpoint I guess because so far I'm not getting much help other than people saying that it could be a number of things. I think in my case it's under watering as the two plants that are showing yellow spots has got a lot less water, my biggest fear is that the two plants are infected and could they possibly spread to the other plants? so I'm thinking should I remove them or not?
I will keep an i on your thread to see if you have better luck receiving help.