Bigdawwg: You should have done your homework before you planted your seeds. I don't work in Celcius but as I recall your 15 to 16 degrees is pretty close to freezing. Our guidelines are a low 65 degrees F at night and ideally no higher than 75 in the day time. In dirt I've grown up to 80 degrees in the day time without a problem but temperature has a lot to do with growth rate.
Light is also relevant. I grow under T-5 fluorescent lamps with 5,000K for veg and 2,700K for flowering. I use a progressive light schedule I learned about at school that starts with 20 hours of light and 4 hours of resting darkness and I drop the light by one hour each week. I think you need to RTFB before you go any further.
1. Read: SeeMoreBud’s book, “MARIJUANA BUDS FOR LESS- GROW 8 OZ. OF BUDS FOR LESS THAN $100.”
2. Read: Jorge Cervantes’s book, “MARIJUANA HORTICULTURE THE INDOOR/OUTDOOR MEDICAL GROWER’S BIBLE.”
3. Read: Ed Rosenthal’s, “MARIJUANA GROWER’S HANDBOOK.”
4. You’ll also want to read: Mc Carthy’s book, “GROWING MARIJUANA.”
5. You should also subscribe to, “HIGH TIMES,” magazine. Each issue is chocked full of useful information. .” All these resources are very well written, well illustrated and packed with information that will answer most of your questions before you know to ask them. And I want to add a new book to the list, a 6[SUP]th[/SUP] one: “THE CANNABIS GROW BIBLE- SECOND EDITION,” written by Greg Green. It’s a match to, if not better than, the ones listed above. Doing your homework and consulting these resources will save you and your plants a lot of anxiety before you plant. These forums are great but often they can’t get the information you need to you in a timely fashion. I hope this helps. HSA