yellowing leaves please help.

So i put my clones in 4.5 inch pots with fox farms light warrior soil on the 17th.

My fire og and master bubba kush are doing great, they have no yellowing or anything. The Plants with the problem are my two gods gift plants, they're way shorter and are both showing yellowing leaves on the bottom. I

ve been using bottled water(crystal geyser) since i don't have a RO filter. So far all ive used is straight water and a mix with Humboldt roots. Could it be that i need cal mag and or sea mag?

Yellowing leaves on the older lower leaves are a sigh of N deficiency. If you haven't fed yet it is time to start. If the plants are not well rooted yet start with 1/4 strength and work up to the final rate a little each watering. When the plants are rooted to the sides and bottom of the pot you can water with epsom salts at a rate of 1/2 tsp /gal of water. This will provide all the Mg you need for the whole grow. No need to buy those expensive chemicals if you want to use Mg.

Time for Nitrogen now.

You can simply get a 20-20-20 water soluble plant fert. Use it at 1/2 strength. Works every time for me. Use it once every 1-2 weeks. Do not over feed.