Help! Droopy & sad tomato plant

Grateful for any ideas/help about my sad little "Early Girl" tomato plant that was transplanted 2wk ago initially seemed fine, normal watering, but this week droopy, soft, limp with some yellow spots on leaves (see photos). Sprayed diluted vinegar last week to ward off aphids. Soil by finger dip feels cool, slightly moist but not soggy but I'm halting watering for now. Gets decent sun, here in California (no recent rain). My other cherry tomato doing OK behind it, though Celebrity also mildly droopy. Thinking of trying some hydrogen peroxide?  Thanks for any help!