The yellowing could be a number of things.
First, I noticed you used Miracle Grow. Miracle Grow is terrible, I don't care what anyone says...it's garbage.
Second, the yellowing could a Nitrogen deficiency. So, be sure that the nute your adding is High is nitrogen, IMO. That miracle grow soil does not come as carefully PH and nute balanced as higher end soil.
Third, all of the distilled water I've tested is pretty acidic...like 6.0 range. I've read many different opinions regarding optimal PH, but I believe that the PH needs to be higher than regular, untreated distilled water. So, you might want to get a PH water test kit, and PH increaser from Petsmart.
Hope this helps...the size of that flower pot concerns me regarding root growth, they don't have much room to dig. Good luck to you brother and I'll be watching. Keep pics coming.