If you can procure a small heater with thermostate and set it at 25 deg celcius would be preferable. It's also important to have higher humidity in the vegetative stage at approximately 60%. Your night time temperature shouldn't dip below 18 deg celcius either. Lo siento por mi español, sólo sé muy poco.

You can try turning on your lights during the coldest part of the day. You can also buy a small heater and warm up the space around your tent or grow room.

Any heat source means spending watts on heating, it's better to spend that on more lights. I'm in winter here and have ambient temperatures even lower than yours and I keep them above 25°C. What I recommend is to heat the indoor with the heat that the lights dissipate; to achieve this, you need to reduce the extraction from the indoor. For 400 watts and an ambient temperature of 5°C, use an extraction of 35 CFM (50 if you use a carbon filter), that will allow you to have a temperature inside the indoor close to 25°C. Second, in winter, plant autoflowering strains in 24/0, that way the lights heat the indoor all day. Good luck.