I have heard start low like 1/8 of what the bottle tells you for you age plant. Now with a PPM watch and see are the plant drinking more water (ppm's will go up) or are they drinking the nutes (ppm's will go down). If you start to see burns from the nutes flush or add water to delute.
now with that said Iam only about 1 month into DWC myself but that is the info I have found and makes sence.
Currently my (2) 25 day old plants from seeds have 100ppm of foxfarm big grow/big bloom, and the plants are drinking more water then nutes so I watered down the nutes by adding 1 gallon distilled/phed water droping the ppm to 90. The strain that iam growing is easy to burn so iam going to play it safe the whole way.
Hope this helps and I wish I could remember the persons name that passed this info on to me.
take care and good luck.
