I'm just popping in for the firsts time but yes, indeed excessive nitrogen will inhibit rooting- the VERY simplified version of what the NPK is for... N=leaves. P=Roots n buds. K=Immune system and flowering. Don't give plants Nitrogen while they are still rooting; it makes them want to grow leaves instead. All they need is hormone and water at that point, and taking cuts off a plant that has been given a LOT of N recently also isn't all that great.