What deficiency is this?

You seem to be giving a huge amount of epsom salts in relation to the plant size. At this size, they only need tiny quantities.

I’ve had a similar issue with my RQS Royal AK Auto. The soil was too hot (too heavy on nutes) with initial runoff 2000 ppm / pH 8, so on the first week I attempted to flush it heavily with FlashClean and pH 5.5 to get rid of excess nutes and lower pH. She was quite small, the pot was final (10L). On the second week or so she had a similar pattern on the leaves, the light was at about 15 DLI. I proceeded watering her with pH 5.5 almost until the end, when finally runoff pH became acceptable, and she boosted immediately. So my guess this is a pH and/or overwatering issue.

You should indicate your light info too like distance and intensity. Are all of your plants affected or just 1?

Need more info and perhaps additional pictures. Just looking at the one pic your soil looks really wet. Thats a no no. Have you fed the plant? Do you pH your water correctly? Whats your environment numbers?