I have similar plants as yours: buce, java fern and anubia. I use superglue to attach to rock. I don't think you have too much light, just out of balance nutrients. Fish food is rich in nitrogen and phosphate, but lack potassium, bio available iron, and some micro nutrients. So you need to supplement with potassium, chelated iron and micro nutrients or else your plants will not do well.
Diatom is normal in newly planted tank and will go away on its own after settling down. A school of bristlenose plecos will help.