Definitely a good observation. Genuinely hope lighting is the issue, so much easier to fix than remounting everything. I'm just a little skeptical because of the rampant encrusting and the fact that I've seen tanks with very similar lighting and solid growth in even higher par. Fishofhex also uses XR15's with a couple T5's and has excellent growth in colonies up to 6-700 par. He has a 12 hour photoperiod and a 1 hour each ramp up/down. I believe he uses a seneye to measure par if that's relevant.Yeah, it was more of a general observation of the overall trend of the ones that are growing (the opposite would be if there were a few frags at the very top of the rockwork that were growing up/branching). From what I see... next to the slimer, some branches are popping from that one pinkish/neon green frag, orange hasn't encrusted (are those thicker branches new growth?), bonsai looking one encrusted, a few branches (is that new growth?). When were they put in compared to the rest?
And then finally... since they are different types, maybe where one type is stunted, the other thrived - but again, since ALL the ones receiving highest light seem stunted, just food for thought.
Another reason I think the issue is at least partially due to the stems is an overgrown frag rack of mine. Everything is completely encrusted onto the rack and touching its neighbor. Got all kinds of frags (oregon tort, pink floyd, pikachu, strawberry shortcake, pc rainbow, SCOP, etc). Coincidentally, the only two frags that have started branching are a wwc yellow tip and a birdsnest, which appear to be the only two species that Ryan is getting significant branching growth from. Everything else encrusts rapidly until it touches its neighbors and then just stagnates. I occasionally snip the branches and remount them so they don't kill each other, only to have them repeat the same process and still show no signs of branching. Par is ~250 throughout the whole rack measured with an MQ200. I know, not the best par meter for blues, but it shouldn't be more than ~30% off. Point is its pretty unlikely that I have too much light on this rack and I'm getting shockingly similar results as OP.