Started flower today and having some yellow in the leaves

Just flipped my girls to flower and am starting to have some yellowing starting in my bluenana and I had a nutrient lock out cuz of salt built up on my frosted apricots plant my jeallylicious is fine tho last feeding I watered on day 41 0 ppm water at a ph of 6.74 and my run off was 6.14 and ppm run off was 2240 more then what I fed in the last feeding so ik that my frosted apricots plant had nute lock and I flushed and got it down to 940 ppm then the next day I watered it and the ppm run off was 1050 on day 46 of watering it idk why my ppm are higher the next day after I flush and get them down to about 600-700 ppm I water and check the next day and they went up I'm not adding no more nute I'm watering with distilled water no ppm shouldn't my runoff be lower. I'm using fox farm ocean forest soil in 3 gallon pots a few days ago in day 48 of veg I fed them a little more. I fed each plant 680 ppm at 6.41 ph of nutes i used 1.5 ml calmag 1 tsp big bloom and 1 tsp of grow big. Then I water in day 52 of veg and run off was looking better my jeallylicious was 380 ppm and 6.33ph runoff. The bluenana was was 1150 and 6.03ph run off and the frosted apricots the one I think I had a lock out on was 520 ppm and 6.28 ph runoff then I waited two days for them to drink the water and watered no feeding either in between and checked runoff again and the jellylicious was 6.83 and 720 ppm in my run off, the frosted apricots was 6.73 and 810 ppm run off and bluenana was 6.49 ph and 1090 ppm can someone tell my why my ppm goes up the next in my runoff and I don't feed them any more I just don't understand. Also I just flipped to flower it is day 53 since starting and day one of flower I'm uso fox nute line how much should I be feeding them in the beginning of flower I don't wanna over feed and I don't want them to get hungry til I flush could you experienced growers please give some advice.