Big Bud #2 Lower fan leaves turning yellow then purple. Anybody seen this before?

The lowest fan leaves on my 35 day old big bud #2 started to yellow and then started to turn purple.
I've researched loads and havn't come across anything that describes this hence why i've made this thread.

I germinated the seeds on 1st april using wet tissure in the airing cuboard, then put them into a small six pot propagator tray.
when they had thier 2nd set of proper leaves i then potted on to 4inch pots with a half and half mix of john innes #1 and bio bizz all mix with vermaculite.
The roots filled out the 4inch pots pretty quick so i potted on again into 6inch pots, but this time only had the bio bizz all mix to use.

i'm in the veg stage at 18/6
the set up is a 400w hps, 4inch carbon filter and extractor fan, an RVK one i think. and a small 6inch fan inside the tent.
temps were about 30degrees during lights on but ive got it down to 25 degrees now.
and night time temps are about 17-20 degrees. a few times its fallen to about 15 degrees but not often.
I know cold temps at about 15 degrees can cause purple leaves.....i just don't think that is the case here as the leaves are yellowing first.
the plants are also quite light green.
When the yellowing of the lower fan leaves started i was aware that the all mix is very hot, so i flushed them straight away to try and get rid of some of the nutes in the soil.

i gave the plants 2ml of bio bizz grow two days ago because to me they look deficient in N, but i was wary of doing it as i've only done a few grows and ive never grown any of the strains im doing this time so i dont know how hungry they are etc, so i'm treading lightly.

ive attached some pics of the purple fan leaves i just cut off.
any ideas or advice would be appreciated. thanks!

What are you feeding them? What is the ppm?

havn't been feeding them anything as the bio bizz all mix soil has alot of nutes in. someone told me the all mix is better suited to outdoor grows as it's so hot.
but two days ago i fed them 2ml of the biobizz grow nutes in a litre of water because the plants look lighter then they should. so i wanted to give them a little bit of N to see if they would perk up a bit.

if its lower fan leaves and your plant is in flower this is normal the plant is just sucking up all the energy from the nutes in bigger fan leaves.

do any of you actually read what i wrote? i have written what stage i am at. the plants are 35 days old....in veg....

The EC of All Mix is too high for smaller plants in veg. I reckon that the soil had a much higher PH than ur feeding programme and burnt them.

~If you go check the bag the EC will be on it - Bet it's quite high. All mix is more concentrated than the light mix.

Hope this helps.

ps - if this is the case then back of the nutes and water with run off.

i read somewhere that the PH of the all mix is 6.5/6.6. I was aware that the all mix is too hot for younger plants but it's all i had. was just baffled by the purpling of the lowest fan leaves. so you think it's the soil being too hot that's causing the problem? I did give them a really good flushing as soon as they started yellowing to try and get rid of the nutes in the soil a bit.
I always water till run off so there isn't as much of a salt build up in the soil.
I don't actually bother with PH at the moment as i don't have a PH reader for the run off, but i think i'm gonna invest in one. could this possibly be a lockout caused by the all mix?

the biobizz all mix is..... EC: 2.4 - pH 6.2-6.6.

also there is no tip burn on any of the leaves, not even a slightly yellow tip to indicate nute burn.

ShowMeTheWay said:

the biobizz all mix is..... EC: 2.4 - pH 6.2-6.6.

Click to expand...

This is why. EC 2.4 is for adult/ larger plants for flowering. If u didn't have anything else then u could have flushed the soil with plain water before use.

The soil has too much N P K ( EC 2.4 ) it is not the PH. The nutes in the soil have done this.

ok cool, i'm going to repot into final 5L pots on tuesday with john innes #3 so hopefully they will bounce back and with that soil i can control the nutes more myself.
thanks for the help/advice i appreciate it mate.
so i guess the purple is from way too much P in the soil.

actually just reading up on john innes#3, they say its pretty hot too, would i be better off with john innes #2?

Just check the EC on the bag and look for EC 0.8 - 1.0 for plants that are 10 cm - 25 cm tall. After this height (30cm) they should be able to handle a higher EC as they have a denser root system and are hungrier.

ok cool cheers

You have got the information you need to get you on the right track now. Just wanted to straighten you out though, that is NOT purple!

this is taken form a cannabis deficiency guide:

"Phosphorus (P) is necessary for photosynthesis and works as a catalyst for energy transfer within the plant. Phosphorus helps build strong roots and is vital for flower and seed production. Highest levels of phosphorus are used during germination, seedling growth and flowering. Deficiencies will show in older leaves first. Leaves turn deep green on a uniformly smaller, stunted plant. Leaves show brown or purple spots NOTE: Phosphorus fluctuates when concentrated and combined with calcium. "

Your first line of defense should always be a deficiency guide. Its hard to give too much P as cannabis plants love P in all stages of growth.

And at slanty...I would have to disagree, them leaves are showing hues of purple, they have brown spots and the whole leaf is necrotic, classic signs of a P deficiency.

post of pic of the whole plant. It helps besides just the leaves pics.

ShowMeTheWay said:

the biobizz all mix is..... EC: 2.4 - pH 6.2-6.6.

Click to expand...

They're 5 weeks old since germination and in super strong soil. Nute burn is my vote. At 5 weeks, mine would be in seedmix and then Canna soil 0.8 - 1.0 EC.

A pic of the whole plant would help tho.

I used all mix and didn't get this problem, Post a pic of the whole plant, Lets have a better look! I did get yellowing of the bottom leaves though when they was ready for bigger pots?

Looks and sounds like a P and N deficiency...I would start to slowly introduce veg nutes as you are doing......