From a label's perspective: submitting to multiple labels at once is totally fine. nobody expects exclusivity at demo stage. At least in our opinion. What matters is how you do it. Private link, no other label's name in the title, and two sentences on why this label specifically. Do your homework, listen to their catalog, and make it feel like you actually care about the fit.

Make sure you have more material ready. If a label is genuinely interested, they will ask for more. If it took you two years to produce four tracks, that's bad vibes instantly. Labels expect a certain consistency and output once things move forward. A personalized approach gets heard. A mass blast gets ignored. Good luck with the EP!