This resembles abiotic damage (an issue caused by environmental conditions and not a pest or disease), but we can't be certain. Was the plant recently put outdoors from spending time inside, or was it in a greenhouse at the nursery? Usually, cold damage from near-freezing overnight temperatures cause this kind of leaf blanching. Tomatoes, basil, and many warm-season vegetables and some herbs are sensitive to chilly temperatures and sometimes get put outdoors too early; we did have several late-spring cold snaps this season. The yellowing and eventual shedding of leaves with lots of tissue damage is a normal response by the plant, and new growth should be able to replace lost leaves. Leaf tissue can't heal from injuries like this, but the plant can drop any leaves that are too badly injured.

Keep an eye on the younger new growth at the top of the stem; it should remain undamaged if this is not an infection. If it does develop spotting, please send us additional photos of the new symptoms and we'll reassess its diagnosis. In the meantime, you can transplant the tomato into the ground now (or into a larger container if you were going to grow it in a pot) since the temperatures have moderated.

Miri