Seems to me it could be a couple of things, one some tomatoes just tend to wilt in the middle of the day, see if it is wilting when it is cooler out, 2 you had a late frost that got the plant tips, or 3 you are over watering.
You could prune them and they would grow again or just leave them a little longer and see if they recover after you check the three things above.

tom,

Is perhaps your ground waterlogged from all the rain we've received lately? I ask b'c with waterlogged soils the plants can't get oxygen or nutrients and so wilt and then the leaves turn yellow.

Also, Yellow Pear is quite susceptible to Early BLight ( A. solani) but you haven't described any lesions on the leaves that go a long with that, and EB doesn't show wilting anyway, as a symptom.

But if we're talking just this yellow Pear and the others of the same variety are fine right now then perhaps one might start thinking about a seedborne disease.

Are all the Yellow Pears being grown in the exact same area and receiving the exact same treatment?

Carolyn

Are all the Yellow Pears being grown in the exact same area and receiving the exact same treatment?

they are all in a row in the back of my garden Carolyn; the ones on the left are ok - the ones on the right ? not so good - i have spotted new growth on one of the ones i "trimmed" - but the other is rapidly declining - i was wondering if i should keep pruning the wilted leaves ? or just pull them ~ Tom