Lyretail Anthias stark behavior change - hiding

[kyl]

Wondering if I've overlooked something, but I've had my previously super active Lyretail Anthias (2, both female about 2" long) become very reclusive and hide in the rock work all day over the past week or so. No visible signs of disease on them, scales look pristine (no spots, dusting or haze) and I don't see any abnormal breathing taking place. They seem to still be eating somewhat and are shuffling about behind the rock work, but previously would run the tank and be out swimming all day. The tank (65g/20g sump) has two small clowns, a cleaner wrasse, the lyretails, an elongate dottyback and bi-colour blenny.

I've tried to keep things as clean as possible, no gear is transferred / used between tanks. Everything wet in there has been QT'd for 7-8 weeks, with fish having an initial TTM, then a 5-6 week stint in QT for prazi & paraguard treatments and observation. Inverts were fallow for a bit over two months, and there are no corals presently.

I did add a bi-colour blenny and red elongate dottyback a bit less than two weeks ago, both of whom went through the full QT regimen. The Blenny was previously in my nano tank (has had a bad dino outbreak in the past) and I've had him for almost a year. Dottyback was picked up very early in November and both fish had shown zero signs of anything throughout two weeks of TTM and almost 6 weeks in QT. All other fish in the tank are acting perfectly normal, and I do not see the dottyback being aggressive with anything which was my first guess for the behavior change. They were all fine together for ~5 days then this hiding behavior started, but the clowns, wrasse and dottyback all remain very active. The blenny sits in his hole or perches on the rocks just as much as he did when in my nano tank, so he looks fine too.

There is one note as it does appear I have dinos in this tank now, which had to have come from my nano somehow (with/on the blenny?). The overflow has been quickly "growing" the characteristic bubbly-snot look and some of the sand is getting stringy, but all water parameters are good (ammonia 0, NO3 3ppm, PO4 ~.03). PH has been dropping to 7.5-7.6 during the day with the heat on, but that has been going on since early December and isn't new.

Just wondering if anyone has any obvious ideas that could be causing the change in their behavior..