Plants wont stretch or get tall ..PLEASE HELP!

Hello, someone please help me figure out my issue. My first 6 runs i never had any issues and now my last 5 runs ive been going crazy and cant figure out why my plants wont get tall. ive had many of my expert growing buddies come to my room and take a look but none seem to figure out what the issue is. My plants are in 8" rockwool from clones under under MH lights. room temp is 77-80. im in 6th week of veg and my plants are about 12-15" tall . i used to never ever have this issue. i dont know what im doing wrong please someone help lol. ive tried different cones from different places with the same outcome.

 

feeding with
Liquid karma 2.5 ml/gal
hygrozyme 2.5 ml/gal
roots 1 ml /gal
verde 1 ml/gal
dark energy 2 ml /gal
pro silicate 3 ml/gal
hydrguard 2ml gal
AB ppms to 900

 

I’ve been doing that and a few of my buddies have been and have seen major success for years. I don’t know what it is about the room that all of sudden changed and now they won’t stretch.

 

Basically nothing has changed that I know of , besides the fact that they won’t get tall. They are nice and green with amazing roots too

 

Anyone?

 

ive used different clones all the time and some even from the same batch my buddy used and he used the same nutes and same schedule but didnt have the issues i have.

 

its mind boggling