Mushrooms are not all that easy to attach. You can try using wedding veil to hold them in place. They will attach on their own in time but keeping them where you want them is not always easy.
You could also try super glue gel but I have little luck with mushrooms and gel glue. They slime too bad.
White thing looks like a sponge but hard to say. Should be no problem.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,