If you would like more then generic advice, give us some details bro. What's your current training setup? (The more detail the better). Whats your current diet like? Are you tracking both workouts, and diet? Using any supplements, protein powder, creatine, anything at all, and if so what is it and how much? Are you using any particular nutrient timing?
If you can fill in some of those details, I know I can maybe give you some great suggestions and many others probably can as well.
There are so many variables for this, that its really hard to say anything of value, without knowing more details. Could be overtraining, could be undertraining, could be too long on the current routine, could be a dietary issue, mineral deficiency. Could be about anything. Would be glad to offer my two cents if you can throw out some details bro.