I am noticing a weird discoloration on one of the ...

You should check your PH levels. Unless I'm running a monocrop (an entire room of the same keeper pheno started in clone form) I like to run a fluctuating PH schedule with my grows. Different strains and different phenos from strains will feed differently and you need to maintain a propper PH level so the nutrients you're feeding can be made available to the plant. So I alternate PH with each water in soil from 6.2/6.5/6.8 and then repeat. Also make sure your lights arent too close to your little ladies. Make sure you're checking the EC/ppms of your water and nutrients before you water to ensure they're in the appropriate range for whatever stage of growth your plants are at. You should also be checking the EC/ppms of your run off when you water so you know what the levels are at in your medium. I see you keep your day time and night temps the same. You'll want to start bringing your night time temps down a couple degrees from your day time temps so the plants can transpire while they sleep. Keeping your day/night temps the same makes it hard for your plants to off gas and transpire what they up took during your lights on period. This means they wont uptake as much food or water as your grow progresses. This can slow growth, lead to deficiencies, and unnecessary stress. Hope that helps. 🤘