If you are using multispore, it can be luck of the draw. Take lots of prints in a clean space for the future and give it another go.

Spawning to a bulk substrate might also help with yeild in the future too as might switching to a bulk grain such as rye or bird seed. Generally, the more grain, plant fiber, and available water you feed the mushroom, the better it fruits. Whole grains and a simple bulk substrate like coir and verm is actually less work and less expensive than cakes. Cakes contain very little grain when you think about it.

One other thought could be temperature. If it is winter where you are and your tub is on the floor, the coolness could be effecting them. Cold air results in slow, stunted, fewer, and sometimes deformed mushrooms.

Love your fungus and it will love you back.