Hair loss is may be due to some hormonal or hereditary or some vitamin deficiency.If you notice any area of balding spots,that is the real hair loss.
In my view whatever shampoo you use you will lose some hair. There are many chemicals in shampoos, some may react /allergic with you skin and cause hair fall,i think that is normal..The normal hair fall per day is 100 strands.
Some procedures such as Ironing,Curling,dandruff,combing wet hair may cause hair fall.This could be the main reason for the hair fall,so we cannot blame on shampoo always...