You could bake bread in that box. I use a horticultural heat mat on a timer for 8-10 hours starting at midnight. The ones I use range 24°C-30°C and are thermostatically controlled to adjust with ambient air temperature.
Full spectrum LED grow lights, 1200 Watts set 40-60cm over the soil surface, timer as well set 12 hrs. ON beginning at 0600 - as much as an average Spring day cycle. The average room temperature is ~20°C, could drop as low as 10°C. LED’s are much hotter than many suspect.
I cover seed sets until the seed leaves are green and first adult leaf buds appear then remove clear plastic cover. Soil is always moist, mist twice per day and bottom water in tray. I start in March, plant outside in May. Location New York City, USA. Current outdoor temperature is 0.6°C.
Keep the lights - lose the box