Based on your ICP, it looks like you are low on trace elements ( Ni, Mo, V, Zn, Mn ). Iron reads 0, but that is expected as it's optimal level is too low to be detected. Your Iodine is also a bit low.
Ok, here is my take on trace elements, and please understand this is all anecdotal. Trace elements are notoriously difficult to measure and maintain. Until ICP testing, most of them were basically unable to be measured. Corals can withstand trace element deficiencies up to a point. With habitually low (or zero) trace elements, corals will eventually run out of trace elements and problems will set in. The opposite is also true, raising trace elements back to normal levels will eventually restore corals trace element reserves and help them to recover. The normally prescribed method of maintaining trace elements is regular water changes. However, the tendency towards growing Chaeto as an export mechanism, can leave certain trace elements deficient due to chaeto's uptake of those specifically.
What to do in your case? There are 2 products on the market that may help. Either of these would be a good starting point to see if your trace elements being deficient are the problem.
The first product is E.S.V B-Ionic Transition Elements. This will raise your Iron, Manganese and Zinc. This is targeted at trace elements that get used up quickly in the water column, which corals need to grow. Two of the traces (Iron and Manganese) are also important for chaeto growth. Trying this out for a few weeks or months would be a good first step to see if your corals are simply depleted of trace elements. Note the Plus version of Transition Elements includes some carbon dosing, so unless you are trying to lower nitrate and phosphate, you may want top try the version without carbon dosing. This product will not add Nickel, Molybdenum or Vanadium, all of which you appear to be low on, but if the health of your corals improves while on it, it will confirm that it is a trace element issue.
The second product is Brightwell Chaeto Grow. Where the E.S.V additive was targeted at only a few important traces, this one covers a broad range of traces. Basically everything that chaeto needs to grow. The thinking is that this product will prevent chaeto from depleting important traces when used as an export mechanism.
Both of these products would require ICP testing to determine if the levels are increasing or are stable. I would suggest following the dosing instructions on the product closely and doing subsequent ICP tests to determine if the dose is too high or low.
Personally, I would try the Transition Elements for several weeks and see if your corals improve as it has very targeted traces that both your corals and chaeto require. If that works, you will at least have confirmation that it is the deficient trace elements that are causing you an issue and you can explore all the ways of maintaining trace elements. There are other trace element products on the market that can help to maintain trace elements (Red Sea Coral Colors is a popular choice).
Hope this helps.
, but for others). One way to tell that this is occurring, is that your corals will not brown out even with the high nutrients. In fact the opposite happens, they get pale and start to starve. Just be aware, that when you do dose iron in these situations, your corals are going to see a sudden surge in nutrients as they will suddenly be able to use the elevated nitrate and phosphate. This can also cause issues and losses for corals.
