There's a pretty direct relationship between aggression and temperature (as well as temperature and metabolism).
My experience with growing baby Haits is pretty limited but I had pretty good luck raising and keeping slightly larger Haits (and Cubans) at lower temps (upper 70s / low 80s).
I also observed some Haits over time in a LFS a couple of years ago. The store got probably 6-8 1.5" or so Haits in...added them to a 20L (if I recall)...with caves, java moss,etc. Tank was probably mid-70s. Probably fed flake once per day. And who knows how frequently water changes were done. Anyway, at least some of the baby Haits were in there for a couple of months...and I don't recall any of them experiencing bloat or bloat-like issues (not that I saw them every day...but it's pretty obvious). This overcrowding might have reduced the aggression on any particular fish (or maybe they sold the biggest / most aggressive ones first).
Anyway, what I took away from it is that bloat is most likely caused by instra-specific aggression / stress probably coupled with power-feeding high protein foods (and stress + heavy food = gastric problems). Lower them temp a bit, feed less often (maybe once per day skipping a day or two per week...and less high protein - Haits are omnivores) and see if that makes a difference. If there's a particular fish that's beating on the rest, divide him right away. A 75g should be large enough for awhile, but won't be forever (unless you divide a pair).
Matt
