Couple probs w/ pics PLEASE HELP

ok so heres the deal on 1 of my plants i have had this yellowing problem of the bigger fan leaves only on the lower part of the plant at first i thought it was nute burn so i cut the nutes out completely and flushed for about 2 weeks it stopped for like a week then the problem came back ... i still am not using nutes and going on like 4 weeks now i just recently transplanted from a 2gallon pot to a 5gallon pot and added new soil (but the same its been in so no stress should occur) its growing fine but i still have this yellowing problem this is my first grow and idk if its my watering cycle i have red that overwatering will do it but i know that i dont overwater my plants due to the fact that i use .5l twice daily and foliar feed so i dont think there should be any watering issue due to the fact that i use so little so the roots will stretch during the day... here are some pics ........ thats the first plant........

Now to the second also was having this problem with the second but i transplanted it from a 5gal pot into the ground (it was in different dirt that was to tight) and it corrected the prob i have no more yellowing but i go outside today and we been having this heat wave and i noticed the leaves are folding up like a venus fly trap... now 2 things i heard that this can happen due to Mg deficiancy and/or lockup or is it just because its to hot? i really think im just paranoid because of my first grow and im making these problems bigger than what they are but i have gotten this far i dont want anything to happen =) lol here are some pics... ........

K so i hope i explained well enough to get some help thank you for everyone looking at this and please any info at all is helpfull like i said its my first grow so im sure i got plenty of knowledge to absorb.
i should also mention the the first plant problem might not seem severe but 4 of the fan leaves have turned bannana yellow and i cut them off so its working its way up the plant. also my next 2 questions i have started flowering was wondering how long it will take, the plant is bagseed from supposidly purple kush (who knows...) and should i just let it flower and do nothing about it? or should i address this prob? thanks again everyone.

nothing to worry about mate they look healthy keep it up.

nute burn will look like your plant got burned. And when that happens I flush, give it half dose nutrients next watering, then resume feeding schedule (which for me is feed every other watering). If you cut out nutes you're gonna have deficiencies.

What nutrients & water you using and do you check ph?

A lot of nutrients lack magnesium or calcium so those are common deficiencies.

i unfortunatly dont look at my PH which i probably should and thats my own stupidity but as for nutes im using miracle grow single watering can packets but like i said i stopped using them about 4weeks ago because A: i heard miracle grow is terrible to use and very harsh on plants, B: i just started the flowering process this week and the nutes i have are high in N about 25-10-18, and i heard during flowering you want lower N and higher P so im in need of new nutes i think but was also wondering if i start new nutes that are different IE: tiger bloom will that stress the plant because its never had it before? should i just leave it be and finish the flower and harvest? thanks again

I personally don't believe switching nute brands will stress the plant, but changing NPK amounts might.

if you're using distilled or Reverse Osmosis water without a bunch of additives, your PH normally will be fine. But my tap water here has a PH of 8+ and that will really cause problems.

Miracle Grow gets dissed a lot but I think it's not bad for beginners. I never had any problems with it, you just have to supplement calcium and magnesium. Cus MG doesn't have one or both of these micro nutrients. Never used the single watering can packets or know what they are but i've had success (very healthy plants) with the water soluble Miracle Grow All Purpose Plant food and Bloom Booster.
At full strength I feed 1 tsp per gallon every other watering. You can increase by a little more until you see tip burn and then back off.

Oh yea you should definitely get a fert with very little N. Too much N in bloom will cause slow flowering and low yields... and harsh smoking weed.

thanks for the advice very helpfull