This post is going to be a bit different from the others.
First all the stuff about adding more CUC members and/or algae eating fish is nice, but it's not going to solve that big a problem by itself,
Second, in my opinion you have way too many fish in the system. More to the point, you have 2 tangs and a foxface, These fish tend to produce a lot of waste produces. I would recommend you remove one or two of the tangs or foxface and about 1/3 of the other fish.
Third, any ammonia reading other than 0 is a problem in a reef, but it may be your test kit. Get a quality test kit and retest. If it's not 0 look for problems. You may have something the died in the LR.
I also recommend doing the following -
Cut way back on your feeding.
Make regular water changes.
Run GFO (Phosban or equivalent) in the system. A reactor for this is a help.
Raise your lighting to reduce light for the time being. This is not a long term fix, but slows regrowth down.
Re do the LR so it's a open as possible and gets circulation. Yea, it's a big job, but you only need do it once.