How much are you giving them when you water? The plants look hungry, and I don’t feel like they should this soon after mixing in that soil conditioner.
How often should I water and how much water should I put in 3 gallon pots ?
I’m not really sure how the miracle grow behaves, but with most soils pots should get a good soaking, then be allowed to dry out before watering again. Every 4 days doesn’t seem unreasonable if you are completely soaking the pot. But if you’re just wetting the top of soil that’s probably not often enough.
I may have been mistaken about your media too, are these still in the miracle grow?
Yes they are still in the miracle grow soil
Problems seem to be in line with others I have seen try to use it.
Could be a bunch of things. Are you check ph and ppm of your water? Do you know what ph is recommended for soil you are using? How about checking ppm in and out? Some of the leaves look burnt like too much nutrients and others more like a deficiency. Could be that neither are really the case and you just have a ph issue.
I commented earlier that they looked under watered, are you soaking the pots when you water and then allowing to dry out some?
I am going to agree with @dbrn32. Looks as though you may be experiencing some nutrient lockout. You may have answered the question earlier but I am on my phone and can’t scroll back. What is the pH of the water you are using?
Okay just scrolled back. At pH above 7 the nutrients are locked out from the plants. Do you have a pH meter?
BTW I used miracle grow potting soil for my first grow.
The brown spots could be a calcium magnesium deficiency. Yellowing is typically lack of nitrogen. Drooping could be from underwatering. I am NO expert by far but I have lived through the same issues.
Best to you my friend.