Could you tell us what kind of soil/medium is? What are your lights, and their distance from plants? Are the Temps and humidity good, and fairly consistent? What type of fertilizer/soil amendments do you use? Do you have a way to test the PH of your soil? What type of water do you use? Do you know it's ph, or if it has chlorine in it. Lots of questions I know, and maybe you can't answer all, but the more people here know, the more likely someone may help you avoid future problems.
I know how you feel Dimi. I had times where I had beautiful plants, I was so proud, then one problem or another would show up and the harvest either never happened, or were less than ideal. It can really make you want to quit or convince yourself you aren't smart or good enough. It's not true. I think most people either don't give their plants enough love, and some give them way too much. Sometimes less is more. 1 person says use this product, someone else says also use this, and that. Before you know it you've got 15 different things in your soil, some fighting each other,when really only 2 or 3 of those products are needed. I've found simple is better usually. That's why I've been growing plants in pure worm castings, or pure cow manure, or pure compost, then testing them together, then with a new amendment, etc etc. Really I just love doing 100 tests to keep me busy, but the goal is to see how little I can get away with while making great plants. Complex grows can be very fun too, I just want to find some of the simplest to maybe pass on what I learn to those who like things some, don't have much time, or much money,and,because I'm just weird and don't like following the crowd. It's more fun to make my own soils and do things my own way based off experience, not what people say is right or wrong.
I've rambled. My point is, be careful you aren't making your grow too complicated for your abilities. When first reading about growing cannabis it was overwhelming how many products people use and how perfect they say everything must be. Now I find I can basically grow them like any garden plant. Fairly simple ingredients, I don't ph my water, measure ppm of anything. Eventually you just look at your plant and know if it needs water or food, has root problems etc. I don't see spending 50% more money for 15% more yield lol.
I wish you much luck and I hope you can provide information that will help others help you. Keep your head up. It gets easier I swear!