I have said this many times. The most important thing a new grower should know is to not over love your plants. If you think it needs water wait a day or two. If you think they need their first feeding, wait a week or so. That soil has time released nutrients in it. This is why I never use a medium with nutrients already in it. I want total control. Anyway, I would wait until the plant shows signs of needing Nitrogen, then start the feeding. When this happens, the leafs will start turning a lighter green, and if left unchecked to long a yellow.
So I think you started feeding them to soon, and water them to often. Next time you water them give them a good heavy watering, then mark that day on the calendar. Do not water the plant until it just starts to wilt a little. If it took 5 days, then water then every 3 1/2 days. if it took 7 days, water them every 5 days. Most failures by new growers is from just loving their plants to death. Lay back on the nutrients, go slow.
And Yes, I hate Miracle Grow soils. I think they named it that because it is a miracle anything will grow in it. But i have know a few people that can grow the DANK in it. but most of them go about a months before they give them their first feeding. And only about 1/4 str for that one.
I would suggested you allow you plant to dry out until it just starts to wilt. so you can understand how long of time this is.
Good luck on your crop.