top leaves and bottom leaves curled under and a bit yellow

This is my first post so bear with me I have grown several times, but it has been years and a lot has changed with new nutes. I have a 600 hps/mh bulb. I ran the mh during veg and switched it over. I am using foz farm nutes. my plants were lush and green during veg and nice fan leaves. I transfered them into 3 gallon bags. I am three weeks into 12/12 about 2 weeks since pistals forming. I have two plants out of nine that have yellow leaves and browning at the bottom. I thought they might have nute burn at first, so I flushed plants. I then spoke to guy at store and he told me it could be opposite. I am using tiger bloom, big bloom, and big bud, every other watering. I need to get ph tester. two plants have yellow small new leaves at top and all leaves are curled down, not up. Other plants look great. I moved up my lamp bc I thought it was two close, about 12 inches it is now at 20. I also thought about transfering the two plants, into new containers perhaps 5 gallons? I flushed them all, then after speaking to the guy, I went back on my feeding schedule. It looks like the tops of the two plants have dry leaves and bud is stunted? I am trying to eliminate variables but don't want more problems. I will post pics but any help would be great. Also I don't mind if flowering period takes longer if I transfer, just want to correct problem. Temps and humidity are fine. Thanks

ok its been three days since flush and I moved the light last night, I am already noticing a difference with new grow seems better and not curled up. Do I go with regular water one more time, then a light nute mix? Also can I still transfer the plants into larger pots, even though i am two weeks into flowering? Will the top cola that got heat burn grow back? thanks alot