Overwatering
Here is what I try to teach newer growers for proper watering techniques. When you go to water/feed your plants, make sure you saturate the entire pot. Generally folks look for about 10% runoff. This means you want 10% of what you put in, to come out the bottom. This means you've successfully saturated the soil in the pot and evenly and completely soaked it.
The important part, is making sure it dries out fairly well. This will happen a little faster in fabric pots as opposed to hard plastic pots, for example.
How do I know when it's dry enough or time to water again?
After watering and completely saturating your soil as mentioned above, pick up the pot. Heft it in your hands a few times. Get an idea of how heavy it feels. Use a scale if you really want to get technical. Do this once every day. Each day you will notice it gets a little lighter. When you go to pick up the pot and it feels super light (like 1/3rd or less of the weight when fully watered) you know it's time, or almost time, to water again.
Another tip is to stick your fingers down into the soil. Stick them in a few inches, down to the middle knuckle on your fingers or 2 or 3 inches deep, and feel for moisture. If you pull your fingers out and they're damp, give it a little more time. If you don't feel any moisture in there, it's time to water again.
The reason being for all of this is because these plants are highly susceptible to root rot and other pathogens in the soil. Stagnant water in the soil is a breeding ground for pathogens and bad bacteria. These plants really like a lot of oxygen in their root zone, and regular cycles of wet and dry help keep your roots healthy and happy.
In my years of experience and giving advice to people on how to grow, this is easily the most common thing people get wrong. So, don't worry so much about how much you're watering at one time. Worry about how often you are watering. Good luck!
