That's your difference bro, it's the added coco and perlite. Perlite is innert where coco alters the cation exchange capacity so can alter the nutrient chemistry. Mixing organics and synthetics with coco, perlite and soil can cause many issues. It looks and sounds to me like the organics are just starting to break down but they are fighting with the synthetics and causing the salt build up when the soil dries out on a hot day. I learnt this the hard way a while ago during the heat using coco and perlite, once they get dry, the salts build up and drop the pH which in turn alters the cation exchange capacity, causing calcium to lock out. Sorry bro, not trying to lecture, just trying to save you going through the same shit i went through. Temperature and moisture are the two main things that alter chemical compounds, you had major changes in both over short periods of time so my well educated guess is that's what's going on. Lots of freshwater will fix it