Priority one should always be >>>> make sure you can keep the root system healthy, because w/o a healthy root system a healthy plant isn't possible. You can battle soils that hold too much water for control over your plant's vitality, or you can choose a soil that allows you to water correctly. Once you have a soil you can water correctly, root health is very easy, and control over nutritional supplementation (fertilizing) also changes from something of a guessing game to something you can precisely control. The appearance of your plants is also a mirror of root health, so once you get the root health thing solved, your plants' appearance will reflect your progress.
.... some basic information at the link below, which will help you avoid all the most common pitfalls that bring growers to the forums seeking remediation.

Al

Here is a link that might be useful: A basic overview

Thank You.