SO SO SORRY to hear that you lost some of the shrimp at the weekend. I am sure many members will feel your pain as probably all of us have been there (me many of times to the point where I gave up for a year). From what you say it looks likely the temperature was the problem otherwise it would be unlikely to have the problems in 2 completely different setups at the same time where they were both doing well before! Fingers crossed that the 2 babies survive.
At least you will be in a better position to get some more shrimps as at least you have the tanks up and running so you shouldn't need to do the pail setup again and won't need to keep adjusting the water parameters as you now have the system steady, and more knowledge and experience. It is better to get the setup up and running before you get the shrimps I assume anyway. You were doing outstanding up to that point and lets face it the weather isn't within your control!
I hope you have some crystal shrimp left as well, to keep you going with both tanks.
YOU CAN'T give up now, New Year coming up, so NEW YEAR, NEW START, SOME NEW SHRIMPS!
We don't have a heat problem over here so I can't help much with advice on that aspect for the future without the chillers etc? I would maybe float a plastic bowl in the tank(s) with some cold water in it from the fridge and maybe drop a couple of ice cubes in the cold water bowl every so often (keep changing the cold water when it warms up from the tank heat), that may work if you don't get long/lots of periods of heat and don't want to bother with chillers etc - that is what I would try IF we ever have that problem, unlikely though - the water is being circulated anyway so I can't see there being a problem with different temperatures around the tank and I assume it is a bit cooler anyway at night as well.
Again, sorry to hear of the disaster, and hope you're not too upset/deflated?
Simon