You'll want to use a nutrient that has a ratio of about 5-2-3 or so for a plant in the vegetative stage. 'Even' ferts won't provide enough nitrogen relative to other components for a rapidly growing annual indoors. Start half what the bottle says and work up.
Post pics if you get a chance; yellowing low leaves can also indicate insufficient light, but have a different 'look' to them than N starved ones.