dry at the base of the stem

That's damping off. so...yeah...very unlikely it survives. Damping off is always watering related (exacerbated by temperature issues).

Also if you can, raise the soil level. This will create more stability and offer a place for more healthy roots to grow.

You can try sprinkling a little cinnamon around her and water in. Antifungal properties...Cheers

(Green forming on the soil)

Hi mate, this looks like some serious overwatering. You can see green forming around the edge of the stem. This is due to the soil not drying out. Only water when the pot feels light. It should take a few days to dry out. I'm in 3 gal pots and its 4-5 days for me. I water 2L and that gives 20% runoff. This is what you should aim for (20% runoff) It looks like you dug up some roots, if that was right before taking the picture it seems like you've got a serious issue and the may not make it.