It does sound like it is getting to cold, the best way that I have seen to keep the temp up is to get one of those liquid filled radiator type space heaters and set it to I guess 22C not sure I am not familiar with celcius. These heaters are very efficiant meaning very low wattage and produce a lower heat that won't shock or burn your plants and are alot less of a fire hazard.

Another way is to go to a 24/0 light cycle for your veg that way your light keeps the room warm until you go to flower. ( I use a 24/0 cycle in my grow during veg.)

LOL and looking good so far.
Jerry Garcia 2007 Reviewed by Jerry Garcia 2007 on . WHITE WIDOW & K2 IN THE SHED Well its been a few months since my last harvest of K2 and they were spot on. i had 2 k2 seeds left and i got 10 White widow seeds from the dam. I germinated them last week 5 white widow and 1 of the k2 seeds popped i have transferred them to pots and they have broke soil into 6 nice little seedlings. Ive got a 400w MH system over them soil is peat moss with a mix of perlite an vermaculite ratio 1/4 parts perl +verm to3/4 peat. ive been using superthrive since germination. The rest of the Rating: 5