Have you tried Spectracide at all? I can't remember, but I had the best luck flooding with that. Sorry to read it's RAs. Over half my seed starts have died within a week due to what I believe is a pythium/fusarium infection, began while I was out of town in Portland helping my husband with his mom's stuff (diabetic, just had a leg amputated, in rehab, etc).
I went with Triazicide because of the PHI. I can't remember, but do you add in stuff like aspirin to help boost their immune systems? I found it only marginally helpful, but a bit helpful nonetheless.
Honestly, I hope to NEVER have to deal with RAs again, nor russet hemp mites or broad mites. This wilt crap is bad enough, fortunately I have friends to fall back on for new cuts. This may be the first year ever that I'm not able to do my own seed starts, though.
Maybe it's time to dial down the lights a bit, if infested the plants aren't going to photosynthesize/utilize nutrients as vigorously anyway. It only just occurred to me that I put stressed plants under partial shade, like under a tree or in the greenhouse, and it often helps. <shrug> Just throwing it out there for consideration. Never had a chance to do the hot water thing, and 135*F seems pretty hot to me, but if a plant is looking like a goner maybe it's worth the sacrifice to give it a whirl anyway.