Scalp Issue

I've been having this issue with my scalp for some time now. It looks like it's dry/flaky in certain parts and other parts look red/irritated. I'm not putting anything bad in my hair or using cheap shampoo. I've tried to dandruff shampoos but I'm beginning to think its not that because the problem persists. Should I buy a filter shower head? Maybe it's the water in my area lol I literally have no clue and have looked up tons on Google. It just gives me bs. If you have experienced this please give me advice. Some shampoos I've used: Paul Mitchell, Bioterra, Bamboo, Clear (target), Clairol Hair Food clarifying.