Ok would you please explain why "you don't need to adjust pH"? I'm just trying to understand your reasoning behind this. Thanks in advance.
Organic mediums such as peat and compost will buffer pH. I have always grown in peat based mediums and never once have I had to adjust the pH or my water, but my water is good anyway. In England there is an impending ban on the sale of peat based soil, I have been experimenting with peat free mediums and it fucked up, due to pH.
To the OP, you are growing Autos. In my experience, Autos need a fraction of the feeding that a photo period plant does. When I grow Autos I will give plain water until they start to flower, just letting them feed from what is in the soil. Then once they have started to flower they will get a dose of CalMag, as my water has none, then feed them a basic Tomato feed at 50% strength weekly. I will then let the plants tell me if I need to up the strength of the feed.