Entering Week 6 of Flower

Plants are budding well and these leaves came of the second most budded plant imo here are some leaves I cut off today. Not sure what is the problem? I make sure ph is between 6.6-6.8 in FFOF and in soil with hydrotron bottom. Would appreciate some opinions on what is wrong? Leaning towards phosphorous Def in late stage???

These leaves have been sitting out for a couple hrs.

Standard Nute Burn ..Flush with 3 times the volume of the pot, with air temperate Ph neutral water, allow to recover in dim light, one day or overnight......avoid feeding for 2 weeks then resume at half the current rate only resume, when you see a positive improvement. FFOF should be diluted with 30-50% perlite to avoid moment like these, red stems may well indicate low temps at night ...keep an eye on your temps

Thank you much for the insight. I am glad its not a deficiency. Since I am in week 6 Should I just Flush the rest of the term on these plants? Also I cant really avoid feeding them for 2 weeks because they need fed every 3 days, I am assuming you meant 2 weeks without nutes. I don't think my temps are dropping that dramatically, when I open tent to change humidifier each day temps are never under 70, when lights on temps range from 78-82 well within acceptable range. I wouldn't think less then 10 degree difference would hurt the plants that much. I will take advice and flush for the next couple weeks.