I don't think the width would be a problem. It's probably more an issue of the weather and possibly the condition of the soil in the beds. One thing you could try in the future is the use of row cover, like Reemay, to retain more heat.

Thanks kudzu

Is there a reason the beds are so narrow? Making them a little wider would give you more options for plant spacing. But I don't see any problems with it - I am just curious.

Just part of how I want to arrange the garden - I don't have much space to work with. The idea for the narrow planters is to just have one row of plants unless I'm doing something really small like radishes.

Actually, part of the original reason I did that was to minimize weeds, because our yard has always been hopelessly overrun. I figured less surface area = less weeds to deal with. Now that I've done it, I've found that pouring boiling water over the soil I fill the planter with and adding a thick layer of bagged soil from the store on top keeps the weeds down to a manageable number, and I expect a larger planter won't be too much trouble.

Thanks for answering my curiosity. For weeds, I think raised beds are pretty manageable overall. They tend not to be so hard to keep up. For space, it seems to me you'd get more bang for your buck if you make the beds a little wider so you don't have so much aisle space. But you can't go to far wrong. Raised beds are awesome pretty much no matter how you slice them!