This week has been a bit strange ... the first days of the week I kept the period of 18h of light, and on Wednesday I changed it to 12. I wanted to have done it a little before but I missed the opportunity. They take a few days with the 12/12 period and still show almost no signs of flowering. So I tell it as a week of vegetation.
About the temp. i recommend you to use what I used on my shrooms : Peltier.
You may buy a cheap water pump of 1/8 and plug to a Aluminum block and make the water circulate within the buckets. At the aluminum you put the Peltier (with a good thermal paste that's essential) and fix very tight, and at the hot side of peltier a good and large PC heatsink with a good cooler.
The Peltier makes the block cold, the water pass within and goes to the bucket making it cold. The peltier has two side, the chill and the hot, at the hot you must dissipate the heat otherwise it wont chill. SO... Chill it outside from your tent.
You must note that the pump shouldn't be much higher than the bucket. A 1/8 cheap pump could only lift the water around 1.5m, and that makes it loses the power of circulate water.
So:
Peltier (around 9 amperes would be enough for each tank)
Heatsink with cooler
Water pump 1/8
Aluminum block
12v power supply
And if it get too cold get an "W1209" and put the thermostat inside the water so it will turn off the peltier (if you install that way) when reach the temperature that you desire.
Colder water is best for the roots.
Good luck, any help just ask.