This jacket is treated with a DWR (durable water repellancy) coating which causes the water to bead up. Over time, and depending on use, the DWR can wear off and dark spots may appear. For example, if you use the jacket for commuting with a backpack, you might notice these spots where the straps touch the jacket. If you use the jacket off the bike or while in the car, you might see dark spots on the sleeve cuffs or elbows. However, dirt on the exterior can also obstruct the DWR.
Therefore, I would first suggest that you wash the jacket as per the care instructions on the inside label. Make sure that the jacket is rinsed well so there is no left over soap residue and then put it in the dryer on low heat as the heat from the dryer will help to redistribute and reinvigorate the DWR. You can find out more info at:
Should you need to retreat the jacket, you want to use a durable water repellency spray. Just do not use a waterproofer that you pour into the washing machine as you only want to add water repellency to the outside, not waterproof the inside of the jacket.
GORE BIKE WEAR