Auto Brooklyn Sunrise

Welcome back to week 3 of this grow diary! Just like the other plant this one is unfortunately presenting with an interveinal chlorosis and also at the end of the week it started developing some brown spots mainly at the leave edges. I’m not really sure what’s going on but I suspect it’s a magnesium deficiency that’s the only thing making sense to me. I had slight problems with adjusting my watering volume and frequency to this new substrate. I overwatered a bit last week because the substrate apparently has a higher water holding capacity. Immediate actions: Less watering, corrugated cardboard under planters for insulation from cold tiles, checked soil PH (slurry test), ordered Epsom salt (should take about a week to arrive) for foliar application. I’m pondering flushing the substrate so that I can be sure it’s not caused by excess of other nutrients and lockout. But since I noticed that the substrate holds water a little bit to well for my taste this could also backfire and further worsen symptoms. Unsure on how to proceed, guess I’ll have to wait for the Epsom salt and try if a foliar spray improves the status of my plants :( Let me know if you have any input on the matter!