Tips on Digitata polyp extension?

[Morpheosz]

I have had this fire digitata for 18 months or so. For the first 6-9 months, it was gorgeous with full polyp extension and it grew quite a bit. Then my tank went through a 2-3 month hardship where things got out of whack and a few corals died back or lost altogether, and during this time the digitata stopped extending. Then for the last 6-9 months or so, everything has been very happy and growing like crazy. The digitata has at least doubled in size in this period so it seems happy but I've had virtually no polyp extension since that period. It looks pretty ugly, in spite of it growing. I have a ton of other coral in the tank and it's all growing quite well. I also have a tabling acro that did the same thing, was super fuzzy for 6 months, died back a bunch, and since has shown no polyp extension but has doubled in size and regrown all the dead stuff and then some. I don't want to mess too much with success because overall the tank is thriving but it's a bummer to have this digitata, which is a centerpiece of the tank, looking so dull. Any suggestions on possible causes / solutions?

Here is a pic of the coral in question plus the overall tank:

 

[Sumbub]

Does it extend during lights out? It's possible that perhaps there's something pecking at them. A fish maybe?

 

[JTP424]

Are they all at the same unextended length? or are there areas that are just not as extended? (see question above )

Also found an old thread that may help:

Which additives for polyp extension and color.

This is a two part question. I'm looking for suggested supplements for improved color and polyp extension. I realize there is not one additive that does both.

www.reef2reef.com

 

[Morpheosz]

Yeah they're all uniformly unextended. There isn't anything picking on them and I haven't added anything between the 6 months they were and since. It's a systemic change that happened when my tank went through its rough patch as far as I can tell.