Marijuana keeps dying

A question from a fellow grower:

I have questions as a first timer which I don’t see in any Google’s I received 20 small plants which I put into pots indoors, I am in winter so not sure this was correct time to be given these, plus I instinctively trimmed leaves dying at bottom, but slowly the whole plant died, etc till I had one taller biggish one which seems to be the only one Happy, could it be that I put a very mild heater that it didn’t like? Will those I cut off just leaving stems due to the fact they all died off, will re grow? I am good with garden plants but this I’d very different, now I was given two new bigger ones same as the only survived plant I see they are fuller, I am not sure if male or female, but they have already shown growth at the top because its pale green, unless I am mistaken, I have not over watered, I am too scared to cut off bottom leaves because all my 20 plants died and now I see the bottoms are looking unhappy, also what are those look like hairs? What does a flower look like?

What are the temperatures in your grow space?

What are you growing the plants in?

Are you giving the plants nutrients?

Are htese plants from seed? or: Clones?

Would love to help you outm but We need more information as to why you are killing all your plants. Or; Why they are dying. If you put a heater in a small grow space, and it causes the air to be extremem\ly dry; You could dry up the plants; Unless you kept them well watered.