possible phosferus defficiancy maybe other issues too?

I'm pretty new to growing and did the classic mistake of trying to do to much in one go, so this poor autoflower has had PH down (the hydro version dur!) nilnat (for fungus gnats) seaweed extract and plant magic, all mixed into tap water (I'm on the coast so our waters naturally very chalky) all poured onto a peatfree organic soil mixed with perlite, the ph is currently in the high 7s (according to my shitty ph meter).
anyways she's looking proper stunted, some leaves have completely yellowed and dried up, some of the top ones are going red on their tips, my last auto also went out this way + I wound up getting a misrable 10 grams off the entire plant - pls help me avoid this again - how do I treat this!
peace

How often do you feed and how strong. What ph water do you feed em? I've heard not to expect great harvests from autos.

First I would invest in a liquid PH meter and it is alright to use hydro ph down in soil. PH adjust your water/feed to 6.5. I personally hate soil testers. They are horribly inaccurate unless you buy the really good ones and if you are keeping the stuff going in ph controlled they are unnecessary.

Im prolly watering about every 4 days or so, adding nutes every other water, everyones telling me not to use the soil based tester, can anyone recomend a budget meter - are those ph pens for swimming pools any good?

NB I also need to know a fix for the phosferous deficiency - is it literally just a matter of fixing the pH? and also, if the current soil pH is 7.7 surely the water will need to be closer to 5.5 to get it adjusted to 6.5?

Bumpbabybump

I've been using the Milwaukee Instruments pH600AQ pen (http://www.amazon.com/gp/product/B005H78ZI0/ref=oh_details_o04_s00_i00?ie=UTF8&psc=1) for a few months now and haven't had any problems. I would suggest getting some pH calibration fluid (I use General Hydroponics 4.01 and 7.0) for it as well because you'll need to make sure it's calibarted correctly. Finally, pH Up or pH Down solution depending on where your measurements come in. I've heard you can use vinegar (down) or baking soda (up). Though, I haven't tried these methods. Measure the pH after you've added all of your nutrients for best results.