Hey Mand. How's it going today?

Your plants look lovely, and the discolorations are nothing to kill yourself over just yet. They could probably be attributed to a magnesium deficiency as Swizzy stated, so some Epsom salt should do the trick. If the leaves start to curl in wards -- maybe twist at the ends -- it's probably just that. Just keep a close eye on them like you've been doing, every thing's going great.