They'd certainly prefer warmer; 55 degrees is pretty cool. How much heat are they getting from their grow lights?

I have my seedlings in my partially finished, but not heated, basement here in NJ. Temps hover around 60 to 65 (MAX). Dips below 60 on really cold nights. My plants seem to be doing fine under my T12 lights.

Here is a link that might be useful: Luke's SF Victory Garden

My tomato and pepper seedlings began thier life in my cold garage. Down to the mid 40's. They did splendidly. Your temps are just fine.

I have my maters and some pepper plants in the unheated sun porch.
I have recorded temps down to 43 degrees some morning this past month.
I keep the lights on for warmth on cloudy days and let them dry out between waterings they are doing excellent.

Hey, I'm reviving this thread with another question. I would like to start some native perennials from seed. My seeds will need to be cold-stratified which I will do in the frig. I would also like to use my unheated basement. It sounds like slow germination is the biggest issue with a colder area. What do you all think of letting the seed germinate upstairs then moving them to the basement under a light?