Plants deteriorating rapidly, pls help

Thanks ever so much. I moved the light to around 70cm. However, I also noticed my nutrients (Advanced Nutrients Big Bud Coco) were a SUPPLEMENT rather than a complete feed. So, I suspect they're also very undernourished. I fed them some basic plant feed last night and this morning they already look better. I think it was close - another day or so and I may not have been able to rescue them. I'll let the soil dry and I've read about the importance of run off. So, I'll crack on :) This community is GREAT!!!!! Thanks everyone!

In coco, ph needs to be 5.5 to 6.0 with 5.8 being the best for very cycle. From sprout, you can feed at 400 ppm 0.8 ec and increase by 100 ppm 0.2 ec every week if you see good growth. The white tips and curling, canoeing was from the light to close