I think that's why your lower leaves are turning yellow like that. It starts at the tips and works its way in until the whole leaf eventually turns yellow and dies. Make sure the soil is dry before watering. You can't really control the rain, unless you move it onto the porch or something, but you can control how much you hand water. The best way is to do the lift test. It takes a little practice, but once you get the hang of it, you'll never have to worry about over/under watering again. Dry soil is fairly light, so every day pick up the whole container and take notice to the weight. If it still seems relatively heavy, then the soil still has plenty of water since water is fairly dense. Now I'm not saying wait until it's bone dry and wilting, but you don't want to keep the roots saturated all the time. What's your current watering schedule? If you are watering every day or even every other day that is most likely too much. Cannabis is a plant that tends to prefer a dry/wet cycle.