It is a possibility. the OP should give it a try and put down a healthy layer of manure this winter (that would adjust both the deficiency and the pH). Is the soil clay? If so, the peat can provide early growing room. But more important, I have had a number of situations with greens (like tatsoi, chard, beet, cardoon, some cabbages and bok choi) where they stalled and remained miserable. The causes I came up with (I have sandy loam) were too little watering in the early going, too little manure (humus and nitrogen) and too early-too late planting. These little plants are fairly heavy feeders after all. Then there are bug cycles. It looks like the miserable one ran into a generation or two of caterpillars. If they get clipped when they are young, they will never develop properly.
Right now I have two one foot sqaure patches of broccoli rabe. They are separated by two feet, same bed, soil, and watering. One is three times the size of the other, which is next to a stand of lemon balm. It could be a bad companion, or it could be rodent tunnels underneath.
Single fixes do not often work in a garden. Systematic trials starting from optimal conditions (late summer planting in Jiffy pots, high water and manure) should allow the OP to find out how much he can get away with. Hey, it takes five years to figure out how to manage a particular garden.
