hi there glad to see that you are enjoying back the hobby =)
well..frankly mind me but here are some advices
-try to run an FR with Phospate remover to eradicate those diatoms and algaes,your tank would look at its best without them
-upgrade your air-driven skimmer to a better one..if you are going on a budget u can go for weipro..the air driven skimmer wont serve u well for long-term
-try to hunt out the mantis shrimp..it may kill your other livestock in future
-the first "soft-coral" in the shape of a bubble is not a soft coral.its a LPS..yupp and its name is also "bubble coral" =)
-the second "soft-coral" is also an LPS it is called "Hammer Coral"
-your harlequin shrimp looks cool..but i've read somewhere that brittle starfish are not its proper diet so avoid feeding it...switch to linkia starfish instead..
hope i helped a little one way or another
-your mushroom looks stressed and bleached..try your best to nurse it back to its brightful colours =)