I water my large pothos every 10 days and my smaller one about every 7 days. The best way to know if your plant needs water, is to use your finger to feel the soil. Stick your finger down the side of the container and feel down an inch or two. A yellow leaf is an indication you need to water more often. After you water your pothos lift the pot and feel how heavy it is. Now when it becomes light weight again, you use your finger to l manage watering.
Your mint plant has to acclimate to the outdoors very slowly because its used to a greenhouse or shade cloth and not used to direct sun. If you put it in the wrong spot without acclimating it, it will suffer.