SG, do you have a good feel for how heavily populated each species is? I'm no expert, but I imagine if you have high numbers of GSH and HBG, they both could be hammering your YP fry. If your SMB are recruiting, their juveniles could also put pressure on the YP fry, and obviously the adult SMB would continue to put pressure on the YP that made it through to fingerling-juvenile sizes. Even the adult YP will likely eat YoY YP.

Just my novice opinion, but if you've had successful egg laying and hatches in previous years, you likely still have good enough conditions for egg laying and hatches now. The only culprits for your poor recruitment that I can imagine are 1) predation or 2) starvation of fry due to way too many fry overeating the zooplankton food source, if you get "too good" of a hatch.

I don't know your situation and goals that well, but I'd guess the poor recruitment is more likely due to predation. If you have high numbers of HBG and larger GSH, and really want to boost your YP recruitment, I'll just note that my feed-trained YP are pretty good at eating cut bait (1/4" strips of BG)... So, I think/suspect that you could help the situation by trapping and angling to remove as many of the HBG as you're willing to part with, and maybe even larger GSH if you think you have high enough numbers of them to sustain a good forage population. I mention my experience with feeding cut bait as an option to convert some of that biomass of HBG and GSH removed into bigger SMB/HSB/YP or whatever other target species that are feed-trained.