Please Help! Purple under leafs!

I just started growing some Nirvana Bubblelicious. They are only about 1 week old and they are turning dark purple under the leafs but not on the top. Is this normal?

Has it been raining in your area?

did u use nutes on it ?

No it has not been raining at all. I have 5 of them and they all look healthy but that one is the only one turning purple.

Nah man I don't use any nutes I only use water. Keepin it green, but yeah I have five of them and that one is the only one turning purple.