Anyone knows what disease Is that?

Could be disease could be water spots. If it was a photo plant trim affected area use an organic treatment (Maggie organic pest a disease. Spray as soon as you light cuts off let dry 3 day straight the. Every 7 days for 3-4 weeks. U be fine. If an Auto stressing it out trimming will more than likely stunt you plant. Spray it down with organic spray. With lights off ( light toxicity ) follow above instructions

possibly watering habits.. maybe need to add nutes a week sooner. 1) water entire pot - never partially water. you don't pick the volume. you use what it takes to fully saturate it with a little runoff to be certain. 2) wait for appropriate dryback and repeat. high water capacity substrates you wait for top 1" to dry. lower capacity substrates, like coco coir base, you wait for top layer to change color and repeat. I that doesn't sound familar, then it could have been your watering habits. you want a good wet-dry cycle occuring - no wilt of course.

hey, looks like Mag deficiency, i recommend trying Cal-Mag

Hello there good looking plant it is actually doing quite well If the spots are kinda old then I wld think it's old light damage or super small nutrients burn if you have been useing nutrients Also is it possible when you watered you dropped some water on the leaves wile the lights were on? If ypu have not been giving it very many nutrients or none at all yet I would say early signs of either needing nitrogen or cal or some kinda micro nutrients I suggest you take nit at the size of the damage now and keep track of If it gets larger or spreads and how long it takes to get worse. That information will be very helpful of the plant takes a dive quickly Next time you water I would water enough to get a small amount of run off and check the ph level of the water that comes out the bottom of the pot. Make sure to test water that freshly came out the pot, nutrients and stiff can build up and get a off reading if you test water that say has been sitting there for 2 hrs after you watered the plants gets fresh water like fresh pee for a drug test Is it possible your humidity or Temps have been out of range or not going together like 70% humidity is fine if the tent is like 78 80f but if your tent is getting cold at night like 68 70f then you want humidity prob more like 64 65rh also if you humidity has just been super low from the heater in your hz Honestly don't worry to much I think of you keep a good humidity and Temps and give the plant some type of nutrients you will be golden I don't think what's going on with your plant will get much worse