This plant looks like it has nute burn and the pH is probably out... this might be coming from your water.
If you can, try rainwater. Flush the pot and let it drain well... this will help remove excess salts.
Umm If I read right, he said miracle grow. Now my understanding you correctly, you want him to flush it? seems if it was nute burn, that plant will be nuked. JMHO, and not being a dick.
This said get a meter, check your ph, you have 2 known and well documented problems.
1 shitty soil for the plant, yes miracle grow can produce a plant. Is it the wisest and safest, no. Do you have stuff to measure and correct levels? No so move to number 2
2 you have no idea what levels are in the water you are feeding, let alone no idea what the level are when it leaves the bottom of the pot.
An el cheapo ph tester is 7 bucks, a test strip kit is 14, another thought as well, a moisture meter, another whopping 7 bucks. They are not nasa spec, but alot better then picking your ass and wondering. If money is not an object spend a little more for a better unit.
Hope it helped without apearring rude wasnt meant to be.
Edited add on as I made a mistake and well this will explain
Miracle is not really a shit soil, unless used improperly. For best gains you need to know what is going in your plants, and coming out. Hence the ph and moisture meters. Anything less is a guess.
I used african violet mix with good results for starting my seeds. Though after 2 weeks and a few odd days, they went to a mix subcools soil.