I'd go a little higher with the humidity and dampness for a baby. I don't know how you are measuring the humidity, but I don't think that is accurate, unless that entire room is 60-80% humidity all the time. Low sided tubs and sweater boxes are the worst for holding in heat and humidity. They are bad because they do the opposite of what those people say the glass tanks do. You WANT to reduce ventilation and hold in the heat and humidity you are going to all this trouble and expense to generate. Increased ventilation is only good if the incoming air is the correct humidity and temperature. Room air usually isn't.
Its totally normal for the humidity percentage to increase when the temperature drops. Its just physics. Happens in the wild too. Dew point. You can/should leave the lights off at night.
I'm in the process of re-writing the care sheet for Testudo and DTs, but give this one a read through in the meantime. Its going to be different than what you've seen on YT. Keep in mind this was written for tropical species that need higher humidity, warm nights, and eat grass. Other than those three points, most of the info applies to your tortoise too.
The Best Way To Raise A Sulcata, Leopard, Or Star Tortoise
I chose the title of this care sheet very carefully. Are there other ways to raise babies? Yes. Yes there are, but those ways are not as good. What follows is the BEST way, according to 30 years of research and experimentation with hundreds of babies of many species. Babies hatch during the...tortoiseforum.org
So then should i get her a heat mat or lamp??