As a grower, you have to be prepared to kill shit.

I don’t like restricting seedling roots. I’d transplant it soon. Roots are supposed to grow out of the starter media. Clones are different and need a humidity dome unlike seedlings. After you see the few initial roots popping out, you have a few days to acclimate clones out of a humidity dome while the roots continue to develop enough to transplant.

HPS can be cheap to buy up front but buying $100’s of dollars worth of bulbs every few months get’s old. An oil-filled radiant heater is a good option as they don’t produce light for cold nights.