The rocks in the bottom aren't necessary and probably are counter productive. Miracle Grow is way too hot for peppers imo. It tends to burn pepper plants, especially young ones. Don't give them any food for a long time (several months at least) if they're in Miracle Grow because they already have too much. The Miracle Grow probably already has enough food for the whole season, although they may need some calcium and magnesium because MG doesn't seem to have much, and peppers use a lot of it. You can buy something like CalMag+ or make your own calcium/magnesium for a lot cheaper.
I would work on finding a different potting mix for next year. Something like Pro Mix BX, Sunshine, Fox Farms, etc. or make your own, there's a stickied thread at the top with a bunch of mixes and information on making potting mix. They'll do a lot better in one of those than in MG. Fish emulsion, composted manures, bat guano, worm tea, Espoma Garden Tone or Tomato Tone, Dr. Earth are all good fertilizers. Hydro nutrients also work well with potting mix, like Botanicare Pure Blend Pro Gro. I also think giving them seaweed improves the health of the plants. I use Liquid Karma which consists of seaweed, humic acid, sugar, and chelated micronutrients, but you could also make something similar on your own which would most likely be cheaper.
As far as knowing when they're ripe, that's easy, just wait until they reach their final color, that's when they're ripe. To see if they need water just lift up the pot and feel the weight. You'll quickly get used to how much the pots weigh when saturated with water and when dry and you'll know very quickly how much water they're holding and when they need water.
