No nutes at flower inception is not a good idea. I'd give them some grow nutes if I were you. They are hungry as hell. In fact Roseman usually keeps in on veg nutes for the first week or so of flower to support leaf health and has recently add a touch of grow nutes to his flower nutes when he does the switch to try to keep the plant as vegatatively healthy as possible. It is normal for 3-6 leaves to drop per day for the first couple of weeks when going to 12/12 without the extra grow nutes. Good and bad about adding the grow nutes. Plants are healthier but it's hard to get enough light to the lower buds with al the vegatative growth. I'm torn as to what to do myself but decided that I will keep some extra veg nutes for the first 2-3 weeks of flower to try to control the leaf drop but this is purely experimental. If I were you as a first time grower I would keep it simple and give them veg nutes for another week or two and then switch to the big bud nutes.
It's you res temps that would concern me. Got to keep in in the low to mid 70's and sixties are better if you can pull that off. Around 75 you rist some root problems. How are the roots looking?