No smiffy. As calibax has explained the tax code indicates how much income is free of tax, so the lower the tax code the less tax free income there will be. The 'P' suffix indicates that the person is entitled to the higher allowance for people os State retirement age. (This allowance is to be phased out).
Most pensioners' tax codes will change when the State Pension changes, though the increased personal allowance will usually offset any increase to the State Pension. (The State Pension is paid tax free but forms part of your taxable income and the tax code is adjusted to reflect this).
Difficult to say why your husband's code has gone down without further details.