Patchy new leaves - nute burn or something worse?

This is my first grow so I'd appreciate it if someone with more experience could help me out here. I'm growing one NL (the larger one in the pics) and another AK-47, on the balcony and sometimes inside by the window when it is windy. They get a lot of sun here, but it's not a particularly hygienic setup (we have a dog etc.). I move them around the house and eventually to the front balcony to keep them in the sun.

Until last week they were doing really well, they were looking perfectly healthy and growing fast. However, last week I noticed they had thrips (the swarm of ladybirds that arrived alarmed me!). I treated them with a pyrethrin insecticide and that problem appears to have gone, though I'm wary. Anyway, three days ago I fed them (half the normal dose), on
the same day I used the pyrethrin. Since then, new leaves (they're growing suddenly very fast again) have appeared blotchy, not burned or brown, but with lighter and darker patches, not really with any particular pattern (i.e. not just the edges or veins etc.). I was wondering if this is nutrient burn? Or a PH problem? Too much direct sunlight? (average 4-6hrs/day). The tap water here always reeks of chlorine so today I gave them a lot of plain bottled water of PH 6. I don't have a Ph meter, is it worth getting one? Worse still, could it be a virus transmitted by the thrips, or something to do with the pyrethrin?

I should stress that this is only affecting the new leaves. The older ones look as healthy as ever which makes me doubt it's anything to do with the thrips problem. The affected leaves are otherwise ordinary - there's no curling or abnormal growth.

Thank you for reading this and best wishes from Portugal.

usualy when you see yellow leave's it's a nitrogen problem (no Photosynthisis when yellow!) BUT>>> Micro deficiencies show at the top first, while macro appear at the bottom,too many nutrient's show at the tip's of the leaves, too few plant yellow's from bottom up as it uses the nitrogen in these leaves for the top. I hope this help's my friend my eye's suck but my best "guess" is it's lacking in MG or micro nutrient's try a brand you trust and foliar feed (Spray on leaves) quickest solution! Don't go overboard as you can add more as necessary! Hope this help's my friend! jack

organic??? synthetic??...what's your medium(soil)...what did you give them??? half dose of what???...more info is needed..one thing for sure don't feed them anything but water till you know what it is..cause it could work it self out on its own..also your mix looks a little heavy...from what i can see

My fertilizer is NPK 6-3-6,with 6 iron (?). Also contains micronutrients although it doesn't say the quantities. I've always used a half dose of this stuff and as I say, they were perfectly healthy until recently. Although perhaps there was a build-up over time and it became too much? Only the newest leaves are affected, and whilst not exactly yellow in colour, they have light green patches on what otherwise look like healthy leaves. There is no clear pattern of these patches; some leaves are lighter from the bottom and others nearer the top, with no defined distribution.

Medium:
total organic matter 69%;
pH 5.5-6 (too low, no??);
nitrogen 1.33%;
phosphorus 0.7%;
Calcium 2.7%

So I'm thinking now maybe the setup is a bit too acidic? Shouldn't the pH be around 6-6.5 for a soil grow?
Are these images consistent with potential nutrient lockout due to the pH being too low? Or am I simply overfeeding? Sorry for all the questions, I have two females here and I want them to turn out well!

One more thing. They are suddenly growing like crazy. Any association?
Thanks

pH is too low ..add dolomite to soil. Theres a chart under the toxicty sticky that shows lock out pH levels.