Could be many many things...
I would start looking into your lighting, cause there are lots of people with LED issues. IME they started doing really well for a while and then problems would emerge. t5s won't give you such trouble!! :hmm4:
The last picture you posted was too blue...
Problems with bugs will normally come after you somehow introduce in the system. They normally start with the introduced zoas/corals.
Good parameters should have numbers, please.
Dipping should be done accordingly to the specific needs.
Grandis.