SOS Please Help. Unkown problem with leaves SOS

I have 5 plants auto all of them, my first indoor grow. Today is the beging of the second week flowering
The 4 of them are ok but one is having a problem and every day is getting worst.
Few days ago the end of new leaves turned yellow and now all new leaves are like the ones on the pictures (look at pictures 3 and 4)
It is an easyryder from Joint doctor

Ph is 6.4 to 6.8. Temp is around 79-85 F. Humidity 30-40%. Lighting 20/4 430 HPS and 3 hours UVB.

I have no experience from indoor

PLEASE HELP before i start

Im not really sure what that is.. Im a new grower myself.... looking like something to do with Nutes, but i could be wrong.....

raise ur light up further away from the canopy............and also flush with distilled water for a week...............are you misting your plants?

ceeconst said:

raise ur light up further away from the canopy............and also flush with distilled water for a week...............are you misting your plants?

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Thanks bro but i'm not misting at all, the lights are 55 cm away and i use purified water from day one. The yellow curling ends of leaves i think it's magnisium defficincy. I think it is locked out because of sometype of salt. I' m not sure. All 4 plants have same soil and same conditions. Maybe it its genetic.
I've also have check for bugs with my microscope but i found nothing.
If the problem insists i will flush for sure. I didnt do it yet because the plant is growing 1-2 inches per day. Today i gave them only water

try 16 hours of light, plants like to rest too, I have been growing successfully for a long time now and I always go 16 hours not 18, I've tried 18 but doesn't make any difference to my grows. When you say 3 hrs uvb are you telling me that you put heat on your plants in the dark period ? The only way you need uvb is if you are growing in a really cold place. Also if you are going above 6.5 in soil you are depriving your plants of Manganese and Iron Put these things right and ur plants with be fine. See this chart, hydro is on the left and soil is on the right.
View attachment 1559875

maxpesh said:

try 16 hours of light, plants like to rest too, I have been growing successfully for a long time now and I always go 16 hours not 18, I've tried 18 but doesn't make any difference to my grows. When you say 3 hrs uvb are you telling me that you put heat on your plants in the dark period ? The only way you need uvb is if you are growing in a really cold place. Also if you are going above 6.5 in soil you are depriving your plants of Manganese and Iron Put these things right and ur plants with be fine. See this chart, hydro is on the left and soil is on the right.
View attachment 1559875

Click to expand...

Thanks bro. Very helpfull.

UVB is on only during the mid-circle of light for 3 hours. This is not for heat but it's a simulation of the real sun light (in high altitude and lets say Mexico is 4 hours per day) and is increasing TCP. The first weak of veg no UVB (March in nature) and then starting with 30 min to reach 3 or 4 hours on mid-circle of flowering (August in mother nature) and finally no UVB the last 2 weeks (November in natur). HPS lights don't have UVB. Sun has a lot.

The breader says 20/4. That is what i'm doing.

Ph is 6.6 and finally i believe my problem comes from too much P in the soil witch is locking out Mg
Thanks a lot all of you. Look in my active grow for this growing