Good point- you need those leaves on the young plant. Just check the leaves. If the adults are there then you can see them but they will be very small. Like not larger than 1/16 inch long.......and they skin off the surface tissue of the leaf tops. Usually tender, new growth to begin with. They leave a silvery appearance to the leaf surface ............ in small spots.
With plants that young, it will be easy
When I look at your photos and I enlarge them- I can now see the thrip damage. Check it out under magnification. I think it is your call as to whether to spray. If they dont get worse, I would not. If they do then I would spray but just keep an eye on it............... they probably have eggs down and spray will not kill those eggs