I always treated my plants like myself with regard to food. Indians go chewing some newspaper because my cupboards were empty, I either made sure id have food, or if I completely failed on that, which didn't happen, then id just go out to the closest shop and buy some to tide me by.
And if desperate, then have some eggs for breakfast with a pot of tea and chuck the shells and tea leaves on top of the soil. Your mother has probably been doing it for decades. Ive found that for plants, parents are a valuable source of information. They didn't have easy access, the money, or even the availability of magic bottles of nutrients. They tend to know all of the old school feeding methods that don't involve taking the cap off a bottle and pouring some liquid into the watering can.