Dry, brittle hair can be caused by too little moisture or too much protein. You can check your products for protein, and see if using products without it helps. I use rinse out conditioner and leave in conditioner in the morning, and I also spray my hair with a mixture of conditioner and water at night. If your hair is over conditioned, it will become limp or feel greasy, so you will know to cut back on the conditioner.
Experimenting with too many products to name here. All this great info keeps my head spinning.