It can be very difficult near impossible to grow a healthy plant without proper understanding of pH and the tools to monitor and adjust the pH.
A must is a good digital pH meter.
I feel like this should be a sticky. A lot of beginner growers including myself treated pH as an after thought. These days I spend close to an hour carefully testing and adjusting my pH each feeding/watering and my results have improved drastically.
IMO pH issues are the root of almost every mystery problem.