Sick Garden?
 

I have been at our new house for about a year. There is a constant problem which makes me wonder if the garden is generally 'sick.'
Every time I raise plants (tomatoes, basil, foxglove - any soft leaf plant) within a couple of weeks of appearing they develop light-coloured speckles on the upper side of the leaves - see attached photo. This does not appear to be fungal, if anything they look a little scaly. It's particularly depressing to see it on salad leaves.

It happens to plants both in the garden and in new containers where the plants are growing in bought compost. Therefore I suspect something airborne rather thana soil deficiency.

Any ideas??
Thanks in advance.
Lee