please help

Hi all, second year outdoor grower here. I need a little help diagnosing these plants please.
The yellowing started around three weeks ago and the edge and tip about a week ago.
plants are four months old and were doing great up until 3 weeks ago.

I built a temp green house around them as the weather in my area in canada fluctuates from desert to monsoon conditions. I only feed them around three times during veg as they were growing like crazy and now im wondering if its a lack of nute problem, bug, or water issue. i have searched the web long and hard to find pics of leaves similar to mine but havnt come up with anything.
Any help would be greatly appreciated

My initial guess would be over-fertilization based on the burnt leaf tips........what and how much you feeding them?

Looks like magnesium deficiency and calcium deficiency both.

thanks for the quick reply. only fed them 3 to four times during the last 3 1/2 months. Was using general organics, biothrive grow. The strange thing is that i have not fed them anything for around 4 weeks. They started to take over my small shitty greenhouse. 2 are starting to flower and i was going to feed them but i thought i should ask on here before

Ok, dont have any cal mag at home but i will buy some at the shop. If it is a cal or mag deficiency, how long will they bounce back after i treat?

killian123 said:

thanks for the quick reply. only fed them 3 to four times during the last 3 1/2 months. Was using general organics, biothrive grow. The strange thing is that i have not fed them anything for around 4 weeks. They started to take over my small shitty greenhouse. 2 are starting to flower and i was going to feed them but i thought i should ask on here before

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Common for these both to show up early to mid flower.

killian123 said:

Ok, dont have any cal mag at home but i will buy some at the shop. If it is a cal or mag deficiency, how long will they bounce back after i treat?

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The leaves won’t repair. Watch for new damage to make sure you’ve covered it. Usually a teaspoon per gallon is sufficient. Especially if using tap water.

Ok, thanks Hot rod. I have a bottle coming. i need to leave for work tomorrow and was wondering if i could give them a dose of cal mag as well as flowering nutes? Or maybe one thing at a time? never had to use Cal mag before. dont know if it interacts with fert?

Could be PH issue or root lock/bound you don't say how big your pot is but you said plants are 4 months old.

@haily. i thought this may bite me in the ass.... they are in 50 litre pots. did them from seed this year , not clones and should have planted them in bigger pots but i didnt expect them to grow this big and this fast. All four are over 6 ft and i dont know what to do in regards to possibly transplanting?? last week the started showing roots from surface soil. covered them up.
any suggestions?
Should i even attempt a transplant this late?

ph tester is on its way.. i know my well water is high in calcium. ill know this evening

killian123 said:

@haily. i thought this may bite me in the ass.... they are in 50 litre pots. did them from seed this year , not clones and should have planted them in bigger pots but i didnt expect them to grow this big and this fast. All four are over 6 ft and i dont know what to do in regards to possibly transplanting?? last week the started showing roots from surface soil. covered them up.
any suggestions?
Should i even attempt a transplant this late?

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If the roots are coming out the top it may be a problem. Transplanting ir outside to the ground is feasible otherwise I suggest you check out how to root prune and verify it works. From what I have seen they just do some root maintenance/cutting and replant.

Thanks again, I'll have to make a decision on that, just tested my well water and its above 7 on the scale so I'll get some ph down...really freaked out bout transplanting these plants..lesson learned I guess

I could be totally wrong but it kind of happens to me like this. Then the stems went dark purple and the nodes became aggressive and short no fan leaves.