That smell is an indicator of anaerobic microbes - Root Rot. Are your pots sitting above the run-off and are you pumping it away? If the pots are just sitting in the drainage you will have problems with root rot, salt build up and insects. If you have good drainage and the pots are not sitting in water then you are watering too often because that smell does not lie. Get some Botanicare HydroGuard and add 2ml/gallon of nutrients. You need to get this ASAP
It is a constant battle to try to know what and when to add nutrients to precharged media. I don't use it or recommend anyone else to use it. When you start with a blank slate like coco/perlite you know precisely what and when to add.
Fix the root problem first. HydroGuard will clear it up in a couple of days. Be sure you fertigate with balanced nutrients to 15% - 20% run-off to deal with any salt build up.
What you need to learn about watering will come with practice. Here are the basic rules: Never let the soil dry out. Soil and or coco can become hydrophobic if allowed to dry. This means it repels water. This in turn will create dry pockets in the soil and roots there will die. If your soil - coco have accidentally dried out use a surfactant to help re-wet it. I like yucca powder. Don't let soil remain soggy by watering too much too often. Root rot, damping off, molds, fungus gnats and other problems start in soggy soil. When you do water water the entire pot. How to learn when to water starts before you plant the seed. Fill your container with fresh soil/coco and weigh it (heft it) this is the lightest weight and consider it a dry pot. Now slowly water until the soil/coco will no longer absorb the water and run-off begins; weigh the pot (heft it) this is the maximum water, the wettest the pot can get. The difference between wettest and driest is the maximum water weight, for ease of explanation lets just say the water weighs 20 pounds. When the pot loses 10 pounds (half of the water weight) it is time to water again. There is an art to watering.
