Leaf browning

I think you've got a bit of nute burn, mate... Although you don't indicate you're giving any nutrients at the moment, it looks like you've got some nitrogen toxicity - are you growing in too hot a soil? Personally, I would do a flush and run some bloom nutes through with the last gallon of water... Depending on what nutes you're using, the bloom nutes should contain just a touch of nitrogen but not a whole lot which would be ideal, imho.... From experience, I'm going to tell you that you can't rely on those PH strips... it's nigh on to impossible to get any sort of accurate reading when you're trying to match the color with some chart that has been printed... My most urgent advice for you is to invest in a PH pen as it's the single most important tool you can have for any grow - I like Apera although many folks use Blue Lab. I used to use the strips and finally got myself a PH pen and wish I had spent the money WAY earlier - would have saved me time, money, nute deficiencies (if the PH isn't right, your plant is not going to absorb the nutes you provide)... you'll avoid problems to begin with and be able to resolve them far easier if they ever crop up! Good luck! And DO invest in a pen!