What kind of light exactly and what power draw.
But no no problems with 19celcius.
I have 3x 315 watt CMH, 1x 480 watt quantum board, 1x 240 watt quantum board, and 3x 240 watt COB led bars in my 8x8 tent.
My tent gets up to 28c in the day in summer and sometimes 15c at night in the winter. I have 3x6" extraction fans.
2 automatically set for temp and 1 set for humidity at night.
I dont use air conditioning.
I do have 2 little space heaters for nighttime that do their best but with humidity fan kicking in all the time they cant always keep up. My plants don't stunt. They dont stress. They just kill it..
I wouldn't sweat the small stuff brudduh. As long g as your tent sees 18c+ during the day you should be fine. 22 to 25c being the ideal temp. But if its a lil off its not a deal breaker
Invest in automatic controllers. Temp or humidity ones. The ink bird ones work EXTREMELy well and are the cheapest out there that still retain quality. I've got 2 cheaper ones and 1 expensive ink bird humidity/temp controllers and have run them for 2 years with ZERO problems.
Its nice knowing something is taking care of your tent at all times especially when your new to the game