rear axle hub flinging grease on rim and tire, need advice

i have a 2007 attitude fsakg33 fifth wheel, triple axle. i learned years ago about the little rubber cap that comes off the hub and there is a zerk. so i use quality synthetic grease and pump it till it starts oozing out of the bearing. been doing it for years but recently i noticed the grease on my back axle seemed to become very liquid and escape and gets flung all over the rim. i actually had one of the caps come off and that really made a mess. i fixed it though. but i have only noticed it on the back axle, but i also noticed this trip that my trailer brakes aren't working as effectively as they had in the past. see pics. any thoughts from folks?

since it is only the rear axle, on both sides it is odd. been treating all the axle's the same for years. my thought are that maybe the brakes are heating up more and liquifying the grease more so that it can escape the seals,,,,,but i am hoping someone here knows for sure. thanks! please see youtube video of the rims and tires here are two links to the same video https://youtu.be/lMn9JmVLbVE

kevin's rear axle rim with grease all over it