Are mites only prone to certain areas or they found throughout the world....also, would a grow be more prone to mites if it's in a basement compared to a bedroom?
I would either toss it or up-pot it out...If they are autos, I would think you would want one plant's roots in there not 2 and making the yield of the main plant be much smaller.
First mistake was using Miracle Grow as the brand of choice.....you may want to check all over the plants for any bugs. Those spots can be signs of mites.
....if transplanted right. The less stress an auto has during a transplant the better. The more time an auto needs to recover, the more it can hurt the final yield.
Like I said....I currently use the TSW myself. I also have built 2 kits for my 4x8 but these lights for being on the cheaper side have grown some of my best flowers to date.