Leaf tops dry, some leaves burnt on sides, and lower leaves yellow and drop. Please help.

Two plants of different strain, grown together under a 600w mh lamp, sprouted from seeds about 70 days ago, and in spite of what i consider long time growing they reached about 50 cm (19.5 in) each. They are on almost 24h lighting, because sometimes i give them couple of hours of rest in the dark. Onle recently they have started to branch from the sides.

Temperature ranges: They are on 28 C (82.5 F) on average, with the absolute peak that happened yesterday only that was 40 (104 F) for breaf period.

Other than their growth being slow (thats my opinion, maybe im wrong, im a newbie) their bottom laves (not all) yellow and die off, that can be seen on this photo in red rectangle


Also, leaf tops on almost every leaf dry, even on very new, and young leaves, seen on these pics in red circle., while in green circle you can see sideburn of the leaf, only found on that particular leaf.


Growing medium: Coco

Fertilizers: BioBizz assortment, including Bio-Heaven, Root-juice, Bio-grow, Alg-a-mic, while Bio-grow being the basic fertilizer with NPK values: 4 - 3 - 6.

I also add CO2 and microorganisms ( voodoo juice ).

Waterin is once a week, when the medium seems dry.

Thanks for reading, i would appreciate any feedback.

Cheers,

Djumbir

Edit: Pics are uploader subsequently since insert image didnt work.

Well 104 is very hot for those plants it could be stress from that. But it looks like nute burn to me, keep your temps from getting that high and do a flush just in case its nute burn. More air flow would be recommended could just be as simple as stagnant heat.

If that doesn't help then check your roots they could just be out growing their containers.

How often do you feed them? To me looks like could be nute burn or deficiency either one. I am thinking maybe deficiency based off the lighter green color in your lower fan leaves. I am a somewhat new grower so take my advice with a grain of salt. Hopefully some more experienced people who stop in to help you out. Either way, they do not appear to be greatly effected. Overall, they look healthy to me. Maybe let the symptoms get a little worst to make it easier to identify? Plus share how often/how much you have been feeding them and that should help make it easier to identify.

Best of luck!

Thanks guys for the replys. I feed them once per week, i use recommended dosage. The leaf tops seem to dry a bit more than when i took the pics. I spray leaves with alg-a-mic, once every two weeks, and that makes leaves look very healthy, howver, the drying persists. 29 C is the average as i said, however it does have brief peaks with abouve 35 c, but not for long and not often.

Hmm, The single lower leaf die off is normal/common. Not a problem.
The tips of the leaves brown, but the rest of the leaf is ok, tells me your running them right at the edge (your pushing them,,,some nutrient makers ratios do that). Not a real problem.
The one leaf with a few spots on the edge is no problem.
Transplant to a bigger pot will help out, or flip them soon as root bound is on the way!
Add a Cal/Mag product to your feeding. Coco needs that, like RO.
A little silica will help with tolerance to short term heat swings.

Your plant looks fine!

As a side bar, I'm interested in your Orchid on the right in pic 1.

Thanks Dr Who, I will try to do what you recommended. They are transplanted in big pots 5 weeks ago, so i will find something bigger. And what do you mean by that to flip them? Also, how do i use silica?

I have uploaded some new pics, plants look a little worse now.

another one

Yeah,,,I see you might be a tick high on the nutrients. Back off like 25% and continue.
I might run a quick flush of straight pH'ed water through it and then reduce the nutrition and continue.
Add the Cal/Mag when you restart.
If you see signs of under feeding increase by 10% and continue. Same? Increase again and till your back to 100% if need be.

I lowered the nutrients by 70% and the plant appears better, with new leaves without burnt tips. @Dr. Who, the orchids i try to flower after almost a year without any flowering, and so far, one of 3 has flowered, but that one is some different variety. Other two still no flowers.

Thanks again guys for help.