Hydrogen peroxide (with citric acid for deep cleaning) will work if you don’t want to use bleach or alcohol.

Some plants have little smell while others are dank. None of us have any idea what you’re growing. Plan for the worst if you have no idea what you’re growing.

You can add more. Ideally you want to start them in the pot they’ll finish in with time released nutrition.

Not much you can do to fix what’s done but you could bend over those tops away from the light.

Bio-Bizz is complete mineral nutrition. You can use supplements like Recharge with Bio-Bizz.