Habanero leaf marks

Hi,

I'm growing some Habanero chili plants, and the seedlings seem to be coming on well.  Well, except for one plant.
 I've been growing them from seed, indoors on a windowsill, for about 3 months.
One of the plants, in fact one of the larger ones, has marks on most of its leaves that look like the chlorophyll pigment is missing. I gather that this can happen if the plant gets too much hot sunshine. But only the one plant has these marks, the other 9 look fine and they are all in the same place. 
Apart from these marks, the plant seems healthy and continues to grow.
I've moved the plant away from the other healthy ones, in case this can spread.
Can anyone please help in identifying what the leaf marks are. 
I have included a couple of pictures.  One of a leaf of the suspect plant and one of some of the healthy unblemished plants.
Many Thanks.

I was afraid that it might be a virus.  So I will probably bin it just to be safe.   
I just hope it's isolated to this single plant.  Perhaps the virus was already present in its seed.

The good thing is that there's no sign on any other plants, and I don't see evidence of aphids infesting any of them. I'll just have to keep a beady eye on them from now on.
Thanks.