Why are my leaves crispy???

First photos are the plant now, the last photo is a shot of the leaves when I first took it home from my grandma who’s been taking care of it before thanksgiving. i did repot it recently after about a month or so of having it (which thank god bc there was a mesh wrap around the base of the plant and the roots didn’t look so hot- black and brittle) and the new growth looks great so far, but the older leaves that were already on the plant when i took it home are getting crispy at the tips and it’s spreading to the middle of the leaf. I’m just worried about it also happening to the new growth if I’m missing a crucial element to growing this plant. Usually I have a grow light on it for 9 hours a day unfortunately it’s not a sansi or anything it’s just a strip of lights but it’s been doing me well so far, the grow light is off in the photos except the last one, but I’ve since increased the brightness a bit. I water when I see the dirt and the leca at the bottom is mostly dry. The new leaves feel sturdier and the older crispy leaves feel paper like. I’m not sure if it was just from changing environments as the crispiness was already developing when I took it home (as seen in the last photo) or what, but this is my only begonia so I’m looking for some help.