Why aren't my plants growing biggeR?

Question from a fellow g rower:

i have 3 plants. I send 2 pics of each one. The first plant has 18
days, i thing its growing well. The second and third plant. There was
putting on big pots since germanitation and looks bath (both) . They are
two little. And turning to yellow. I hope you can help to understand
what is going on.
two plants has 6 weeks all ready. And i dont like. Looks really small.
Super silver haze.
Soil in pot.
Ph, dont now. Use rwgular water after 24 hr. Repost.
Miracle grow (nutrient) 24 8 16.
600w. Mh.
18 hr light, 6 dark.
72f day, 61 nigth.
Humidity na.
Vs: fan.

Soil may be retaining too much water . Looks like your dirt is chunky with bark. Try Mycorrizae, these little babies are miracle workers. Not sure if they will work with Miracle Grow"a chemical nute".