Is this consequence of thirp?

Maybe you overwaterd you plant with too much light 👌🏼

Too much nutrients and/or a soil too wet. Get rig of the bluemat: they're great for watering ornamental plants when you go on holiday, but very tricky to setup with cannabis (I tried). With soil, manual watering by flooding is the most effective method and also the most instructive when you're a beginner, as it teaches you when the soil is dry enough to water. Also, when you prune your plants, the soil should be half dry to limit this type of problem. Flush your plant, it will help you get rid of accumulated residue and thrips larvea. You can use neem oil and soap as suggested by Roberts (or ready to use "water-solube" mix) to spray the soil surface and also the big leaves as flowering has not yet begun. Cover your eyes and respiratory system when using it, and use a dedicated sprayer.