Are you experiencing MILDEW??? Doesn't sound exactly like mold. But I know that mildew can be a fast spreading disease when it takes off and requires either a water/peroxide mixture sprayed on it daily til it is gone, or if the problem is really bad, something like OMRI certified Serenade is a good product. I've had light mildew on leaves once, and I used that product. Killed it right away and stopped from spreading, but it kinda burns what it touches, so I wouldn't spray down the whole plant with something like that. Just the affected areas.
As for fertilizer, 20-20-20 is NOT an ideal base nute for flowering. While you still need some Nitrogen, this is the least important of the three macros. They are going to want a high dose of Phosphorus all throughout, and I've noticed enjoy slightly more Potassium more towards the end. For this, I try to find something balanced as a good base nute to use all throughout, and if I ever need to add a little extra of something specific, I have seperate bottles of more specific blends that I can add to adjust accordingly. Some good bloom ratios that I have are 3-6-5, 0-10-10, 1-7-12 ... You'll notice all have low Nitrogen levels. The first is a good overall ratio from start of bloom til end, and then towards the end when I want to continue feeding good bits of Phosphorus, but now start to increase the Potassium levels a bit more while pretty much cutting off Nitrogen levels so they can focus on bud growth and then start to autumn off and eat their leaves for final energy, I lean more towards the 0-10-10 & 1-7-12.
As for Miracle Grow, know that they truely are meant more for houseplants, tomatoes, ... Cannabis is relatively high maintainence in comparison to any house plant or standard garden vegetable. Honestly, the only success I've had with Miracle Grow was their new organic line. They have some great blood meal (12-0-0) & bone meal (5-12-0) in small $5 bags, and then I have used their organic potting & lawn soils, although those created some huge bug problems for me, had lots of other unwanted things like moss & weeds, and overall just would not recommend using their products unless you are absolutely limited to it and cannot afford to purchase slightly more cannabis specific products.
As for soil PH, there is a chance it could be a little off, but if your PH test strips are showing 7.0 then it sounds like you're in an ideal range. Outdoor soil has many living organisms & natural enzymes that help act as soil buffers and are somewhat self regulating. While the nutes you are using are doubtfully PH balanced, as long as you aren't over feeding, it shouldn't really be throwing your levels off enough to create problems. Although, always keep an eye on this! If PH does become a factor, Garden Lime (also sold as hydrated lime or dolamite) can be spread into your topsoil layer and then water. This will act as a soil neutralizer and help bring soil PH back to 7.0, as well as contains some natural Calcium, Magnesium, ... that are also important micronutrients
As in everything, moderation is key! Make sure to save the last week of your grow cycle for a WATER ONLY flush. That way you can allow your plant to use up all the remaining nutrients in the soil, and then begin eating at it's own fan leaves for final nutrients & energy. This will extract some of those high chemical & chlorophyll levels and use it for energy to create bigger, more potent buds, and while those levels are decreased, this will greatly increase the final aroma & flavor of the bud. It's worth it and will make things much more enjoyable!
Hope this helps! +rep if you like! =)
