Frontloading and kick in time Q.

[BiggerisBetter]

Diet is right on, 250-300 grams of protein, 250-350 Carbs and I'm eating pretty clean.

Umm, you call this a bulking diet?? Not to flame you but if this is your 4th cycle then you should know this is not nearly enough calories.
Protein: 300g *4=1200cal
Carbs: 350g *4=1400cal
Fat: ???
Your only geting 2600cal from carbs and protein, unless you weight 80lb then that could definately be the problem.

 

[Beezers]

BiggerisBetter beat me to it. If you only eating 250-350g of carbs a day that is an indication your calories are very low...TOO LOW. 250-300g of protein is low for being on as the point of AS is the increase in muscle protein synthesis. You're diet is the culprit. As BisB pointed out, you're probably eating 3000 calories daily tops. That certainly will not do the trick on a bulking cycle.