Once you find the right dilution, Miracle Grow All Purpose is fine for veg, but is unusable for flowering under normal growing conditions. If the leaf edges are starting to burn, likely a bit too strong. (Don't know if this is your problem, tho)

When you get flower nutes, it's usually best to go with a 3 part system, made to compliment each other.
With the three part systems you get Growth nutes, Micro nutes, Bloom nutes (G-M-B)
Buying the system (staying within brand) is a great idea, as everyone manufactures their nutes different, with different nutes, metals, additives. Vegging your plant with the vegging nutes from one company, and flowering with flower nutes from another is generally a bad idea. Have heard it is possible that you might double-up in metals or minerals unknowingly, which can cause lock-out or worse.

Altho these ads are almost annoying enough to re-considder my plans, I'll be trying the Canna products that keep flashing all over the site. (it's a two-part system, I believe. You'd still need to get some micronutes) I love my Fox Farms regimen, but three quarters of the way thru the bottle, the flower nutes start to crystalize a bit.