I have two dwarf peaches in pots.  They are mostly in the greenhouse but come outside once the fruit has been picked and before the new buds open (to protect against leaf curl)

One of the trees is looking very unhappy.  It started last year and I thought it was as a result of the dry conditions in the greenhouse had encouraged a spider mite to drape its web across the leaves.  I sprayed regularly and that seemed to help.

This year the problem is much worse as you can see from the photos.  I haven’t been able to find a similar picture on the internet.  Do you know what is causing this and how to deal with it?