Sun scald or ... ??

[GardeningSue]

Hi,

I am currently growing three types of tomatoes in my garden -- WV 63s, OTV Brandywines, and San Marzanos -- and a few days ago, I noticed that (mostly) the youngest top leaves of the WV 63s had some light yellow/white patches. I've looked at all the photos I can find online, and haven't seen anything that looks exactly like it, on the various disease and pest detective sites. I bought seedlings from a good nursery and put them in the ground about five weeks ago, conditioning the soil with only well-cured horse manure. I have not added any fertilizer, and water every other day or so, usually at night (I was away on vacation with a teenage house/garden sitter a couple of weeks ago, though, and am not sure how well she watered . . . ). The problem does not seem to be spreading to the other varieties. All the other plants are full, green, and healthy; the WV 63s are bearing fruit, but are thin and somewhat sparse, especially at the top, where the leaves are yellow/white and curling.

I've attached here a scan I made today of a branch I took from the plant showing the damage. Does anyone know what this might be, and how I might treat it?

Thanks!!!

Sue