Any ideas?

is this in vege? 18h 100% 20" might be too much for some lights. If the light is made to handle 12h and provide 35-40 dli to your space, then you need 2/3rds of that over 18 hours. Could be nute related to. Without your formual, can't comment on that (not dose instructions of wildly variant NPK values of products, but ppm or weighted average ppercentages off the labels relative to dose of product/total dose dissolved) trace element issues are rare, that kinda looks like boron-deficiency. This would be rare.. more likely nute-lockout or pH, and looks like you don't have a pH problem. Again, would need to know ppm breakdown to give a more informed assessment. nodes aren't too tightly packed, so can probably eliminate the light but do look into it... LEaves aren't forming very well so there's something out of balance in your formua. if all you see is 3-5 fingered leaves, that's a sign of a poorly balanced diet.