I do 299g of carbs at 3300 calories, if this was me I would play around with my macros and see if taking in more carbs then protein makes you gain or vice versa. Im not a nutritionist by any means, but I believe that as people of the gym we are in our own way scientists of our bodies. With that being said, I believe that when you find yourself at a plateau and supps arent helping, the best thing to do would be tweak the diet. I hate when people tell me this because I always feel like I am working hard, especially on my diet. But sometimes we miss some things here and there.
Probably a dumb question but would you consider yourself a "hard gainer"? I consider myself to be one, so i do prefer to take a weight gainer rather than a whey protein. Lately I just switch back n forth, when I run out of whey I get a weight gainer then switch back