Its not a must have but it is nice knowing whats going in. i got mine off ebay for under 15$ i think. are you 2 weeks from actually seeing bud or 2 weeks from 12/12. If your two weeks from switching to 12/12 hit them with a very small amount of tiger bloom and load up on the big bloom. your tiger bloom is chemicals but the big bloom is organic and very weak. it says to put a cup of big bloom in when you hit flowering but go less thats a bit excessive and the shit runs out so fast.
Ocean forest is excelent soil. im very pleased with it. how big where your plants when you put them in, and also how old? Age and size will also play an importaint role on how many nutes you want to use. i could only get mine to 34 days of veg before they hit 16 inches and that's basically my cut off for flowering because of the tent. Do some research on strains if you purchased seed. One of the nice things about a PPM meter is you can dial in nutes for your clones and once you work with a strain for an extended period of time, you can get near perfect results.
Im working with 8 strains this run but got a nice amount of clones from the Exile, Super Lemon Haze, Blueberry, and Acapolco Gold. its a bitch trying to keep the canopy even.