You will need a magnifying glass to look for thrips as they are very small and look like dark specks on the tops of the leaves. In my experience with thrips, they start at the bottom of the plant and work their way up the leaves. If you shake the plants you should see some small flying "gnats" around the base of the plants. There is also an outside chance that you have a potassium deficiency since you are in flower. Check for critters first. If none then let us know what kind of soil you are using, and what kind of nutrients as well.
Thank's for quick response. At the beginning when i noticed first golden brown spots appearing on older highest leaf i taught it's naturally getting older and dying as plant has only left 3-4 weeks to flower.Then gradually it spread to another biggest and oldest leaf. It looked like closest leafs to light source developed spots firstly. Now spots appeared on one level beneath leafs and more. Young leafs are looking unaffected.
On second plant which is 1-2weeks younger,i also spotted same spots on one biggest and oldest leaf at the top of the plant.Spots appearing around leaf veins and leaf cracks where gets brown if twisted with fingertips.
I examined leafs with my naked eye (glasses of) :hubba: and could not see anything. There is maybe 5-10 local tiny flies which i noticed but those are living in pot next to it and this plant has no problems with leafs.It's also a different plant from bagseed which does not worries me as it looks not promising at all with tiny buds.
Nutrients; This might be the case as all i used from start was pk13/14 which turned out to be additive of P-K and canna boost which i guess gives boost. Did checked soil PH and it was around 6 which i counted as OK at that time.
Soil; I bought from local garden stuff superstore."Multipurpose compost" for growing from seed and cuttings".
Now I did fair amount late night reading and after i worked out that the two plants that are getting spots had nothing extra added to and the "bagseed" did get some organic nutrients which had N-P-K ratio 6-2-4. This stuff i use for tomatoes and veg. that i grow in garden.It also contains other organically derived trace elements like B Ca Cu Fe Mn.
I do understand that all this situation is pretty messed up now. I did trow in trouble pots the N-P-K nutes about 24 hours ago.Should I wait 4-5days and see if there is an improvement? I also noticed that buds stopped growing as just week ago I was able see progress every day.
I would have to agree that the critters may still be AN issue, if not THE issue. You have to get a magnifying glass to see the thrips as they just look like little dark specks under light(and that is the ones that are mature and dark. the younger thrips are translucent and impossible to see with naked eye). If they aren't a problem now, they will be for the next grow if you don't eradicate them.
However from what you said about the progression and your nutes, I am even more inclined to believe that you do have a deficiency. Adding the extra nutes may help the plant to pick back up and start filling out more. The necrotic damage will not repair itself at this point, but as the nutes wash in to the soil, you should see the new growth and bud growth pick up.
It will take at least a week to see some improvement if the additive hits the need. If you put the additive on top of the soil then you may want to water it in slightly a couple times to get it down to the root area. Its good that the organic nutes have some trace elements as that could also be contributing. The ph is actually a bit low for soil but I doubt at this point that it is the problem. Let us know what you find.
I did a massive battle with thrips a few years back. Took me almost 2 years to get rid of them. And I had to shut down my entire show for a month to do it, no plants living in my grow room. Thrips in my experience, will leave scuzzy white marks on the top of your fan leaves, not the golden-brown you have going on. I would take a hard look at your girls and consider all options.
If it is thrips, the only ones you will probably see will be very small, off-white worm-looking things on the tops of your fan leaves, and occasionally an adult flying around.
In my experience, Pyrethrum bombs will get you a massive leg up on a thrip infestation if that is what you are battling. Good luck.
edit- Just to add, check my avatar for my opinion on thrips! It's a pirate bug shanking a thrip...:hubba: