Thank you...The starfish I'd toss, I keep finding those latched onto my zoanthids. The nudibranchs I'd research but assume that would be quite a risk having in the tank for either eating corals or dying by crawling in your pumps/powerheads. The other one I think is a stomatella snail which are fine, need a better view to be sure though.
That's a gorgeous looking nudibranch.
Most likely: Hypselodoris Maritima ?
The Hypselodoris species tend to specialize in eating sponges. That's what they've been documented to be found and eating on.