leak at connection to drain pipes and Holding tank

It's a Chevy 2011 chassis Coachmen Freelander 21QB don't know if there is a plate somewhere in the vehicle with more information. There is a panel I can remove that gives me limited access. Your photos were helpful I can see I cant simply unbolt the tank and drop it it looks like my best bet at this point is to apply some sort of sealant around the pipe as it passes through plywood to the tank