Yes. You can cut it all off and then go buy some silicone in the tube and make sure it doesn't have any mold resistant stuff in it. To be safe you can get the tubes that say aquarium safe if u can find it. And u gotta let it cure for like 48 hours before doing anything.
Idk if you should tho. If it is mildew than id say you should. It might hold water now but could fail or leak a year down the road
I got GE Silicone I. Didn't get in the tank yet though. Got a little thunderstorm everything is soaked out there. Lots and lots of scraping and cleaning and scraping. I'll lay the new beads in the morning.