Do you increase rent yearly when market allows ?

[Michael Thach]

I got 3 SFH in Texas which have all tenants for nearly a year. The last year rent was little below market value ( like 50 USD below ) .

This years market value had increased by another 50-75 USD. Will you increase the rent and risk to lose the renter or do you increase it ? 

If yes by how much and do you give them a reason for increase ?