Girl Scout Cookies/Ebb & Flow

After FIMing, the plant began to drink less solution and slowed down a bit in growth. I also accidentally damaged one leaf, but I think that it’s not scary. Apparently, FIMing did not give the effect that I expected. Now it seems to me that the growth rate has recovered. Noticed that strange yellow spots appeared on old leaves. Looks like some kind of deficiency, hope this are not insects. Day 24: I still have not completely updated the solution to a new one. Day 25: Ok, I have completely updated the solution, let's see what will happen next Day 28: After the previous replacement of the solution, the plant only got worse, the spots progressed. It became absolutely clear that the plant was experiencing problems. Most likely, this is a lack of calcium, as people answered me in "Grow questions". I am also convinced that this is a calcium deficiency because I use reverse osmosis filtered water. So, I bought a calcium magnesium supplement from GНE and replaced the solution again.