I planted 6 plants, two in each of three containers, about a month ago. [I'm in SoCal and it started to get warmer here very early, though it's been relatively cool lately.] All 6 are heirloom varieties.
All three containers were done with new, exactly the same soil mixtures and are right next to each other, so they appear to get exactly the same sun and temperature exposure. They've been watered the same too. One pot is about 20% smaller than the other two and that pot's plants are not growing much, while the other 4 are growing very well. One of the two plants in the 'stunted' pot seems to have some 'leaf curl'..... the other doesn't. It's hard to believe the 10% difference in container size is the culprit, but ???????