Sounds like you've been over doing it with the fertilizer. When it comes to fertilizer less is more, go real easy with it. I have plants which are over 4 months old and I've only fertilized them twice with 1/2 - 3/4 strength Miracle Gro. The plants in the pics look excellent but I see the pots have only been filled like half full, so in a couple of weeks take the plants out of the pots (with rootball intact), put some soil in the bottom of the pots and then repot the plants so the top of the rootball is almost level with the top of the pot. This will give the roots some extra room to grow so the plants will grow bigger. And go easy with the fertilizer! give them 1/2 strength every 2 to 3 weeks, no more.