If the AP is working fine just brown in color, it's an indication of high concentrations of copper chloride (I and/or II likely II since it's stripping fine).
If adding water produces a white/gray cloud in the solution it's saturated with mostly copper I chloride (bad= add acid/peroxide in the right ratios).
If no white/gray cloud appears, it's saturated with copper II chloride (good= dilute with water if desired).
Brown solution is a pretty good sign no gold is dissolved in the mix, but always test with stannous before cementing. If you want to get the green color to stay pour off half of the solution and cement the copper out with iron. Properly neutralize and dispose of the spent solution after the copper is removed.
For the other half of the solution bubble air through it for 24+hours and/or add acid/peroxide (in the proper ratio) to bring the solution up to volume again. You may get by with just adding water to dilute the AP. If adding water only lightens the color your copper II chloride levels are fine and you won't need any acid or peroxide. If you start seeing the white/gray cloudiness, acid/peroxide is required.
Studying the copper chloride document on my website will help you understand all this.
Steve