Alright well it being an Autoflower completely changes things. What is your light schedule right now and how much light do you have on it? And what kind of lighting? It should only "veg" for 2-3 weeks, then start flowering. If it's been vegging for 4-5 weeks from sprout, it might not be a true Autoflower strain. The flower under any schedule of light whether it's 24-0 or 12-12, most I hear of is 18-6 and sometimes 20-4.
Drainage issue means there is too much watering being held, or not enough. If you water your plant, feel how heavy it is, a couple days later feel it again, see how much lighter it is, then check again a day or two later. It being in a 3g put at 4-5 weeks old and being in that temp, it should be drinking every 3-4 days at least. Try sticking your figure 3-6 inches down see how dry or moist it is. If it's dry it needs water. But I think feeling the water when it's dry and when it's fully watered works best for me.
Since you just fed it, let it take in the nutes the next couple days. If it looks better then just feed normal with water next time. If it looks worse then you will want to flush it completely. Water it with fresh water until the drainage starts turning clear.
