First grow - 3 week old plants, showing some problems on lower leaves

[m621]

Hi,
Wondering if anyone is able to offer any help/advice/diagnosis of the issue I'm having.

3 week old Northern lights, all seemed to be going ok but noticed some silvering on the leaves a couple of days ago - from looking around forums it sounded like I may have thrips (I have some pyrethrum on order)

But last night I noticed some damage to my lower leaf tips, and on the underside of one of the leaves it looks like something has been munching away.

Is the leaf tip damage nute burn? Do I have Thrips (apart from the 'silvering' I haven't actually seen any other signs of insect infestation) Or is this something else? any help appreciated.

Thanks

 

[Squirly_wrath]

I gotta say it doesnt look like thrip damage to me but im not quite sure what it is what are your temps and humidity?