deficiency? help!

I've looked through all the guides and can't come up with an answer. I'm suspect of phosphorus deficiency. Plant is in week 2 of flower under 600 watts of cfl. Grown in pro mix, water ph has been 6.1. Fed as recommended with pure blend grow until two weeks ago when I switched to pure blend bloom. Lower leaves are turning brown/gray and dropping off. Here are a few pictures, if any specific pics are needed I'm happy to take them and upload;

Use a product called Go Green, it treats all common deficiencys and will make your plant healthy as ever even witha bit of a boost, and only costs around $20 a bottle