I have uploaded a few pics of my current grow. As can be well seen, these plants are showing the same problem as the last grow in the pics above. 2 weeks ago I turned off the CO2 and started bringing fresh outside air in via a 400CFM blower since the way the crop is growing it was just a waste of gas.

Pic # 1

These 2 plants (Lemon cush) from seed are 30 days old and about 10" from rim of pot.

Pic # 2
This is a BB plant 5th week flowering.

Pic # 3,4 and 5

Random seeds of unknown strain but more sativa.

I chopped 2 small plants today to check the stem and root ball. The stem color looked fine but there was hardly any root mass at all. Matter of fact, it had not grown much at all, if any on either plant since I transplanted them
5 weeks ago right before flipping to 12/12. There was no slime and what roots there were were not abnormally brown. Just no growth. Any ideas?