First Time Skunk Grower Could Use Guidance

[Mono]

also, on the bigger plant, the leave tips are curling inwards towards the light , i dunno if you can tell from the pics. is this a problem??

Edit: I don't really mean curling forward, its hard to describe but the end of the leaves are raised. From the pics you can see the leaves look jagged, is this normal?

Also, i had a look at this additive Bustan - Toronto Hydroponics Grow Lights Nutrients Hydroponic Supplies Canada

what do you guys think? its pretty cheap and says it will increase yield and protect from heat stress and fungus. Worth it? or just a product that will do nothing in the long run.