First time with micro-tomatoes (Tiny Tim). Not familiar with these imperfections. To a varying extent for each fruit, appears to never fully ripen near blossom-end. Seems visually similar to descriptions of yellow-shoulders or sunscald, but these are indoors, close under standard LED bulbs in clamp-light sockets with aluminum reflectors. In ~1.5 (actual volume) gal pots, in (a better) commercial potting mix (with a bit of gypsum for extra Ca), and fed a dilute complete nutrient mix with each watering.

Pics outside and inside fruit follow.

Thanks.

NOTE: Red Robins grown in same conditions at same time look normal.