looks like it could be nute burn. Probably some fertalizer in the compost. If it gets worse...flush it until the water coming out is clear and repot with more of a regular or organic soil mix and applyu water again over new soil under it comes out of the bottom. The plant will droop a lot after so don't worry. I will come back and feel much better. You wont have to water again for a couple or few days...
Maybe someone else can give some advice as well, but that's what I would do...