Start nuts?

I am growing 2 plants in waterfarms. They are almost 2 weeks old from seed.
One has almost 3 sets of lil leafs and one has two. I am using Ro water.
Should I start the sensi grow, voodoo juice and b52 yet or wait a week.
I tried a week ago giving voodoo juice and b52 at what I'm guessing and thought was quarter strength but the tips started to burn to I changed the res.
Should I start with all of them or just start with a lil voodoo and b52 or just wait another week? My ppm with Ro water is about 40. When I added the nuts that burned a bit it was at 75ppm. Thanks for any info. Growing pineapple express and kandy kush under a 400w mh.

Let your plant get to like 4 or 5 nodes before u start giving it any nutes, otherwise you're probably gonna burn your plant. When it does get to 4 or 5 nodes only start giving it 1/4 strength then work ur way up.