We actually just lost our platinum, our HB cobra, our male cobra, and our tiger cobra, as well as both of my platies since it's gone funky. My HB red cobras are both struggling. So I moved them to my 5.5 for a day or two. (Because it's actually cycled)
We noticed the cloudiness a few days after our heater went crazy to 90*, so hunny took it off completely, dropping it to low 70's.
Wow... Usually the cloudiness is the BB bloom. However there may or may not be something leaching in the tank... BLEACH should never be used on a cartridge IMO as there is no way to actually remove it from the fibres. I don't even use vinegar. I dunk in old fish water, swish it about to remove gunk and put it back in.
There is a chance there are traces of bleach leaking into your tank... Have you tried a new cartridge?
The heater went crazy... Was there any sight, smell, or sound associated with it? Slimy yellow on the surface, burning rubber smell etc?
Can you snip or move some filter media from your cycled tank into the filter of your uncycled 30 gallon? This could help seed it a lot faster. If you moved all the fish into the 5.5 gallon tank you are probably still going to run into ammonia problems as that beneficial bacteria has adapted to cope only with the existing bioload of the tank. If you overloaded it, you are going to get a mini-cycle as it adjusts to the added livestock.
Other than that, really the only course of action is to do very large water changes to keep the ammonia at 0ppm. Test kits aren't that sensitive so even if it seems like that would be counterproductive to feeding your beneficial bacteria, there is enough ammonia floating around to still keep your cycle going.
Using Seachem Prime is something I highly recommend. My goldfish tank had a cycle crash and they went from gasping and being lethargic to back to their normal selves using Prime to detoxify the ammonia. It will give you a false positive, but the ammonia will have been converted into the much less toxic form of ammonium.
Also what is your pH? Guppies thrive with a high pH, and while a higher pH means that ammonia increases in toxicity, it will also encourage faster growth of your beneficial bacteria. As will a higher temperature.
You can use bacteria in a bottle if it gets desperate. There are a couple of brands that people have recommended as being proven or more likely to work.
Sorry to hear about your guppy losses though! My dad stupidly bleached his filter when he gave his goldfish tank to me ages ago and it took a long time for me to get it properly cycled.
No smell or anything, just overheating. His cartridges are a canister of brown balls, and 3 progressively thicker sponges. I had him move one of the sponges from my filters and put it into his cartridge. I already knew about the seeding.
I've told him a THOUSAND times since we got the original guppies NOT to bleach, sterilize, boil, or even rinse in hot water the cartridges. I've explained WHY. I've laid out the ammonia cycle. I wanted to slap him with the cartridges when he told me! ugh!!!!!
And as much as it's hurt, and it's been upsetting, I've told him the same thing every time we lose a fish "THIS IS WHY YOU LISTEN TO ME, AND DON'T STERILIZE THE FILTER!!!"
I made him drain the whole tank, rinse the gravel from any and all debris, hot soak everything that could be soaked (silk plants, the resin decor), and redo it. He bought some start right, and we added that in as well.
The gupps got a quick salt bath, and they're back in the tank, the water is clearing up now.