Small, brown/ rust colored spots on a few leaves

i don;t think it's under-watered. i use 5-gallon plastic containers. organic soil with nothing extra added except for a bit of "golden tree". does have a fan hitting it though.

It looks like a manganese deficiency - usually due to pH issues. https://www.growweedeasy.com/cannabis-plant-problems/manganese-deficiency

Hello Looks like calcium deficiency to me... if you're not feeding any additional calmag supplement I'd say try to feed at least one dose a week and watch for it to stop spreading. I had also heard before that sometimes strong LEDs can increase the need for higher cal/mag/potassium , maybe with the recent light change it's pushing the plant harder and wants you to pump up the doses slightly. 👍 Happy growing.

Hey bro. By chance are you in fabric planters? If so have a look when watering and watch to see if your feed, water, is pouring out the sides of the planter. If so you simply have some dry areas in your root zone and you need to water till you get 20 to 30% runoff. This is common with fabric planters. Cheers friend

slight increase to calcium feeding to compensate for increased transportation.. Your plant is growing faster under the new light I imagine so don't panic and start adding crazy amounts of Calcium.. It's counter productive in a sense to panic.. So just take it slow.. Add a bit more calcium to the next feeding see if she can balance herself out.. Keep in mind this isn't a guarantee of a deficiency.. The increased light causes the plant to "circulate/transport" faster which can look like a deficiency because the foliage doesn't really keep up.. But Cannabis happens to be an exceptionally light loving plant.