just from looking at the photo:
moist cold air
root rot
bad lighting
she does not have the ability to draw food from the soil.
shes lacking in many nutes thus the feeding system is shutting down.
ya gotta shock her so all her systems kick back in.
1. take out the container
2. put plant in room temperature water while you examine and clean the roots. . do your best not the turn the plant upside down.make sure you give her a nice shower and shake her up a little.
3. replant using a mineral rich medium for its stage: in veg stage, use veg food. in flower stage, use flower food.
4. clean the plant up by removing some leaves and some small undergrowth and put her in a spot with IN-DIRECT lighting.
5. OBSERVE and gradually return to full lighting.
** use new soil and a different brand of food.
**** alot of brand product fertilizer on the current market his watered down to shit.