I use agromax uv. Year 4 I think. I turn them on for 4 hours in middle of day, to replicate mid day sun. I began turning them on at the beginning of flower, but seems to change expression of whole garden. It felt like they all changed to a thcv/sativa type high. Ran a quantum kush. Strain is supposed to be calm and for anxiety. But she didnt come out this way. She was upbeat, and more like an aggressive o.g. now I wait until the last 3 weeks. So they express the way they are described to do. Then let the uvb stress the plant. It seems to make tricomes grow longer, and curl in. I wish I took pics. I get sandier baggies, for sure. I have noticed a difference.
Anything closer than 2 foot above canopy burns em, and you, if you are working when they are on. Lol I've burned the back of my neck. You can feel it get hot fast. I will continue to use them. Am also experimenting with thcv expressions using them. I feel they are related.