The mottling in pic 3 does not actually look like a deficiency, but more like variegation. Let's concentrate on the other stuff.
Your potting soil- I imagine it must already contain fertilizer if you are not ferting and the plants are so healthy. It's time to feed. The brown speckles are a potassium deficiency. A foliar feed with a solution of the 'Micro' from the GH 3-part mixed at 1/4 what the bottle says will really help in the short term, and regular feedings with a complete fertilizer contaning micros are important. You may be seeing signs of a K lockout from pH imbalance. Complete a soil runoff test. It doesn't have to be precise; run water through the pot. Test the pH of the water going IN, and of the water coming OUT. Figure out how much and in what direction the water has changed in the process of going through the pot. Post the results. A soil meter type pH tester may not work for this; the GH liquid is like $7 US for a bottle and is perfectly sufficient for a soil grower.
Edges cupping and curling down like that looks to me like you are about due for a larger pot. Margins curling up indicates acute heat stress, and I'm guessing it's most pronounced nearest the lights. Bend those branches away from the lights just enough so that you can hold your hand there and it's still comfortable, not too hot.
Is that one of those fancy houseplant pots that has a built in drip tray? If so, you may need to remove it, since it can clog and prevent drainage and keep oxygen out of the root zone. If you don't want to remove it, drilling extra holes in the sides of the pot will help, but ideally you don't want any chance of soggy nasty sludge in the bottom of the pot.