Hey TheGreenFingers,
it totally depends on what your expectations are.
Your soil holds nutrients for some weeks, i gues it is now about to run out of.
Since they are growing outside and being a photoperiod, they can be growing for several weeks until they are getting into flowering stage ( might be in August)
They will most definitely go larger so i would advice doing some HST and or LST. Ater being almost done growing i would remove many weaker cola's beneeth the plant to
make sure your higher up colas get nicer buds.
I would recommend to buy some nutrients, even if it is just basic feeding growing and flowering nutrients will benefit you big time and they are really cheap compared to additives.
Like i said its just what kind of expectations you have. If you want to grow like this without nutrients, go for it,
if you want bigger plants, more yield, better quality buds, buy some nutrients.
I also advice you to get ph 5.8-6 for growing and 6.3-6.5 for flowering.
Make sure you buy some long sticks to support your plants in later stages ( not now because withouth sticks your stems will get really thick and your plant will love it, unless they are falling down because of the wind haha)
Goodluck growing and ask us everything u need some help :)