First time dealing with whole leaf hops. I racked into a secondary with 2oz of cascade yesterday. Fermentation was slow but active beforehand. After closing it up. Fermentation seemed to stop. I still have a blow down tube on it. Normally I switch to airlock after racking, but I was in a hurry. When I finish up I always pull the tube out and reinsert into sterilized water so I can see the bubble level in the tube easier as it makes it's way back to bubbling out the bottom. After coming back 24 hrs later the level has pulled BACK to flush with the water level. I reinserted again so I could see water level. That was about six hrs ago. Just rechecked and it is back to flush AGAIN. is this the hops absorbing wort? Not causing a vacuum, but possibly negating positive pressure from fermentation? I have. Heck everything for leaks there are none. Hops were vacuum sealed before I placed them in the fermenter. Any help/advice/experience with similar situations would be greatly appreciated.